xiaomi-riva: Add initial support for Redmi 5A

I have created new packages for Xiaomi Redmi 5A (riva), the packages are created from the xiami-rolex packages. What's working?

• Display (partial): x11 is working.
• Wifi: It uses rolex's firmwares.
• Audio: broken
• Touchscreen: works

I have found working and partial working lk2nd variants for it.

• https://github.com/msm8953-mainline/lk2nd - It doesn't support riva officially. But with a new dts it can be started on the device. It cannot boot the device.
• https://github.com/mi-msm8937/lk2nd - It supports the device, i can start it but it cannot boot the device. (I should fix the dts/rules.mk)
• https://github.com/geckyn/lk2nd - With a minimal device dts it can start and boot the device but it is old lk2nd variant.

Maybe in the future it can be used with mainline kernel:

• https://github.com/MrArtemSid/linux-msm89x7 xiaomi-rolex already supported but i have issues with booting on a Redmi 3s which is also supported.
• https://github.com/Lanik123/linux it is newer than linux-msm89x7 (iommu support is WIP) xiaomi-rolex already supported but i have issues with booting on a Redmi 3s which is also supported.

device/testing/device-xiaomi-riva/APKBUILD

+# Maintainer: Barnabas Czeman <trabarni@gmail.com>
+# Reference: <https://postmarketos.org/devicepkg>
+pkgname=device-xiaomi-riva
+pkgdesc="Xiaomi Redmi 5A"
+pkgver=0.1
+pkgrel=0
+url="https://postmarketos.org"
+license="MIT"
+arch="aarch64"
+options="!check !archcheck"
+depends="postmarketos-base linux-xiaomi-riva mkbootimg mdss-fb-init-hack msm-fb-refresher"
+makedepends="devicepkg-dev"
+source="
+	deviceinfo
+	directfbrc
+	fb.modes
+	"
+subpackages="$pkgname-nonfree-firmware:nonfree_firmware"
+
+build() {
+	devicepkg_build $startdir $pkgname
+}
+
+package() {
+	devicepkg_package $startdir $pkgname
+	install -Dm644 "$srcdir"/fb.modes "$pkgdir"/etc/fb.modes
+	install -Dm644 "$srcdir"/directfbrc "$pkgdir"/etc/directfbrc
+
+}
+
+nonfree_firmware() {
+	pkgdesc="Wifi firmware"
+	depends="firmware-xiaomi-riva wcnss-wlan"
+	mkdir "$subpkgdir"
+}
+
+
+sha512sums="
+1db2d85434b41671c204383f90fe6d6dd1e3c7e874f1bb8d5ba6c7cfc61f91866f641bfa8a8d537ae20b7c8cfdbe4975fe98f40f512c50dc7c0b6c767c2dec43  deviceinfo
+3db3ec596e159be926ea2b5b2496c18e9bc7be24a64a232a56c89a0c9ee710aa2efb2b6fa9fc08efa34759e8242e6c629d08a4ce688ec8aa125830717c191515  directfbrc
+024d11176fbd19f98746317b098d0b54236166aa66155cc68ad75a7ce8335999a1a14ed2efc93f9ac4e05fbc787d8bad793efccf813db81aa48fffd1850ec24e  fb.modes
+"