main/postmarketos-upgrade-kernel: fix custom boot partition being ignored (MR 3095)

This code wasn't actually working for me on samsung-m0, so I
investigated and came up with that this fixes it. I'm not sure if you
are supposed to be able to omit the deviceinfo_ prefix? Either way, it
doesn't seem to work, so let's fix it.

Fixes fad7c7ef

main/postmarketos-update-kernel/APKBUILD

 pkgname=postmarketos-update-kernel
-pkgver=0.0.7
+pkgver=0.0.8
 pkgrel=0
 pkgdesc="kernel updater script for postmarketOS"
 url="https://postmarketos.org"
@@ -14,5 +14,5 @@ package() {
 }
 
 sha512sums="
-dae5ab226de812f3368d115a7906e3070929b58a90f428bb65bd60bde46a0802cb56189c4bbf7d686f4cbf3a78c667979080c9a5535244090118b7163362f9aa  update-kernel.sh
+97b8a84db059cc8e3df69d8d187e08067a1015a01f2528287a4036f7f2c5e5c95a5d9fc2c2533cc7484cc896c1e3a664c2273fa34208d89f2561e3dc3a3a911a  update-kernel.sh
 "

main/postmarketos-update-kernel/update-kernel.sh

@@ -45,10 +45,10 @@ update_android_split_kernel_initfs() {
 METHOD=${deviceinfo_flash_method:?}
 case $METHOD in
 	fastboot)
-		update_android_fastboot "${flash_fastboot_partition_kernel:-boot}"
+		update_android_fastboot "${deviceinfo_flash_fastboot_partition_kernel:-boot}"
 		;;
 	heimdall-bootimg)
-		update_android_fastboot "${flash_heimdall_partition_kernel:-KERNEL}"
+		update_android_fastboot "${deviceinfo_flash_heimdall_partition_kernel:-KERNEL}"
 		;;
 	heimdall-isorec)
 		update_android_split_kernel_initfs