[RX51] Add linux-firmware package

This removes the call to `firmware_install` in the APKGBUILD for
linux-nokia-rx51, and adds the `linux-firmware` package as a dependency
for device-nokia-rx51.

There are two immediate benefits for this:
1) wifi now works

2) the FM radio device was causing the boot to take ~2 minutes longer
than it should, now that the firmware is present there's no delay in
initializing this device

device-nokia-rx51/APKBUILD

@@ -5,7 +5,7 @@ pkgdesc="Nokia N900"
 url="https://github.com/postmarketOS"
 arch="noarch"
 license="MIT"
-depends="linux-nokia-rx51 uboot-tools"
+depends="linux-nokia-rx51 uboot-tools linux-firmware"
 makedepends="uboot-tools"
 install=""
 subpackages=""

linux-nokia-rx51/APKBUILD

@@ -20,7 +20,7 @@ case $pkgver in
 	*.*.*)  _kernver=${pkgver%.*};;
 	*.*) _kernver=$pkgver;;
 esac
-pkgrel=2
+pkgrel=3
 arch="armhf"
 pkgdesc="Mainline Linux for the Nokia N900"
 url="https://github.com/pali/linux-n900"
@@ -109,7 +109,7 @@ package() {
 		"$pkgdir/usr/share/kernel/$_flavor/kernel.release"
 
 	cd "$srcdir"/build
-	make -j1 modules_install firmware_install \
+	make -j1 modules_install \
 		ARCH="$_carch" \
 		INSTALL_MOD_PATH="$pkgdir" \
 		|| return 1