device/msm8974*: Generate extlinux.conf

Generate extlinux.conf for msm8974 devices make ability switch to new lk2nd seamlessly.

device/testing/device-fairphone-fp2/APKBUILD

 # Reference: <https://postmarketos.org/devicepkg>
 pkgname=device-fairphone-fp2
 pkgdesc="Fairphone 2"
-pkgver=7
-pkgrel=7
+pkgver=8
+pkgrel=0
 url="https://postmarketos.org"
 license="MIT"
 arch="armv7"
@@ -90,7 +90,7 @@ phosh() {
 }
 
 sha512sums="
-f44cc3b5db025b0df7e3df88561a46b10b8b106e27e5a227ea50b44ebbd91d2986f4eac3a5f1e3cbac2d3a8c119708d22c057bbb9e4fc7b3b9c0c03460f5e850  deviceinfo
+4f662c7c66601a9c277b260cbbd2806d37cdc273f39599bc49bbc0974a8dd6541338f3a4f9ca3758670b72ee56df64ae918781c21b7ee9441cee40408e983196  deviceinfo
 1a99953420a4068c6205dd90015e895909d39011dcc72fd73ac6880920fe4b95fe54377b9d4864a2d4fac56c4334e0c896ba8cc92dea61f93e9384de0998a910  modules-initfs.mainline
 55360b1ba4ddadea341c9edb13c32ba5f19aabf75ab28602f30cfb79b9df8834f115ef979c70569f23ec1293b1fcd408baf320d87803293ce7106bdc73a26c9f  FP2.conf
 b834461c6866bb0c473dd089dd5da641dd42a00f610aad6503117aa50fe6e200db9ad0a264bb609f12350d59faee1f772907bacd75439f702ea7d52f6f85e2b1  hifi