device-raspberry-pi*: fix boot error caused by missing dtb files (!1047)

The upstream linux-rpi package has been modified: the dtb files
are now located in /boot/dtbs.

device/testing/device-raspberry-pi4/APKBUILD

@@ -4,14 +4,14 @@
 pkgname="device-raspberry-pi4"
 pkgdesc="Raspberry Pi 4"
 pkgver=0.1
-pkgrel=2
+pkgrel=3
 url="https://postmarketos.org"
 license="MIT"
 arch="aarch64"
 options="!check !archcheck"
 depends="postmarketos-base raspberrypi-bootloader linux-rpi4"
 makedepends="devicepkg-dev"
-install="$pkgname.post-install"
+install="$pkgname.post-install $pkgname.post-upgrade"
 source="deviceinfo config.txt usercfg.txt cmdline.txt 95-vchiq-permissions.rules"
 
 build() {

device/testing/device-raspberry-pi4/device-raspberry-pi4.post-upgrade

@@ -0,0 +1 @@
+device-raspberry-pi4.post-install