device-pine64-pinetab: disable sysrq (!947)

Headphone output interferes with the serial console on the headphone
jack somehow, as is the case on most other A64-based products from
PINE64.

device/device-pine64-pinetab/APKBUILD

@@ -3,7 +3,7 @@
 pkgname="device-pine64-pinetab"
 pkgdesc="PINE64 PineTab"
 pkgver=0.1
-pkgrel=14
+pkgrel=15
 url="https://postmarketos.org"
 license="MIT"
 arch="aarch64"
@@ -20,6 +20,7 @@ install="$pkgname.post-install"
 source="
 	deviceinfo
 	uboot-script.cmd
+	sysrq.conf
 	sway.conf
 	99-pinetab-keyboard.hwdb
 	weston.ini
@@ -66,6 +67,11 @@ package() {
 	install -Dm644 "$srcdir"/boot.scr \
 		"$pkgdir"/boot/boot.scr
 
+	# Fix "sysrq: HELP..." messages in dmesg while playing audio
+	# (Headphone output interferes with the serial console on the headphone jack)
+	install -D -m644 "$srcdir"/sysrq.conf \
+		"$pkgdir"/etc/sysctl.d/sysrq.conf
+
 	# Fix for the meta key on v1 keyboard dock, probably not needed on newer revisions
 	install -Dm644 "$srcdir"/99-pinetab-keyboard.hwdb \
 		"$pkgdir"/etc/udev/hwdb.d/99-pinetab-keyboard.hwdb
@@ -79,6 +85,7 @@ nonfree_firmware() {
 
 sha512sums="cdcae98f3dbd995689777c44f42749539e7ac17295693e5b64e528bb8b32203ad2a6c75f774ab513779b773793b474c1d3ec53ee25621e2b1d62989772b675c5  deviceinfo
 1f3108007bd443f86ed8af2b2d84705c52ffcf73809a90ef5e4a1f618b73ab39baf8f8139d578c88e66f589464f8c47d53f72bf46f14b8fa78d962ae10d7d6d2  uboot-script.cmd
+f4b5509fd6a8b23f3667f5e7262b3a19c607a37cb9eaf7d0e93eb826d45c26ec12df4810879bacb8e4042bb83cc80b2b436224c8d47b6d67361369a724bbf7ee  sysrq.conf
 9e71c61bfa72b60e749c4dc04f17eb59d25de822765e81e65c937d6be5236d3951a652b69a1ab973abe6add9f34705be5dbaa98bbfa25daf7504dd50b28524c2  sway.conf
 8d1ef04911f1cfa7eda8185f4f4d807af23105a7c8f23d8c18f02afeccd8ab124de70c2e2760c154a3128fe3793447039fb0abf37aa496f597d27051e275033e  99-pinetab-keyboard.hwdb
 6374ef977eab14b71fa88057ebd52ca03035e387e5f41504598a990f24b2e92bccd2db476c545dc541000e08fccdecb6f1cd63e25b5835df706269e0384dacc7  weston.ini

device/device-pine64-pinetab/sysrq.conf

+kernel.sysrq = 0