**/linux-*: update usage of downstreamkernel_prepare helper

[ci:skip-ci]

device/testing/linux-alcatel-pop7lte/APKBUILD

@@ -40,7 +40,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-amazon-tank/APKBUILD

@@ -35,7 +35,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-amazon-thor/APKBUILD

@@ -42,7 +42,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-asus-duma/APKBUILD

@@ -36,7 +36,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-asus-t00f/APKBUILD

@@ -37,7 +37,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-asus-tf101/APKBUILD

@@ -41,7 +41,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-asus-z00t/APKBUILD

@@ -37,7 +37,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-bq-chaozu/APKBUILD

@@ -37,7 +37,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-chuwi-hi10plus/APKBUILD

@@ -28,7 +28,7 @@ builddir="$srcdir/linux-$pkgver"
 prepare() {
 	default_prepare
 	REPLACE_GCCH=0 \
-		downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+		. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-fairphone-fp1/APKBUILD

@@ -32,7 +32,8 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir"/kernel "$_config" "$_carch" "$HOSTCC"
+	builddir="$builddir"/kernel \
+		. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-fairphone-fp2/APKBUILD

@@ -38,7 +38,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-finepower-f1/APKBUILD

@@ -32,7 +32,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-fujitsu-m532/APKBUILD

@@ -35,7 +35,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-google-crosshatch/APKBUILD

@@ -31,7 +31,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-google-glass/APKBUILD

@@ -34,7 +34,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-gp-peak/APKBUILD

@@ -36,7 +36,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-hisense-m470bsa/APKBUILD

@@ -32,7 +32,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-htc-a5ul/APKBUILD

@@ -35,7 +35,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-htc-bravo/APKBUILD

@@ -35,7 +35,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {

device/testing/linux-htc-evita/APKBUILD

@@ -29,7 +29,7 @@ builddir="$srcdir/$_repository-$_commit"
 
 prepare() {
 	default_prepare
-	downstreamkernel_prepare "$srcdir" "$builddir" "$_config" "$_carch" "$HOSTCC"
+	. downstreamkernel_prepare "$HOSTCC"
 }
 
 build() {