amazon-austin: New device based on hexdump0815 and GjergjiFloychi's work

Basic functionality works well, but I'm doing more testing right now to futher explore more functionality.

device/testing/device-amazon-austin/APKBUILD

+# Reference: <https://postmarketos.org/devicepkg>
+pkgname=device-amazon-austin
+pkgdesc="Amazon Fire 7 (2017)"
+pkgver=1
+pkgrel=0
+url="https://postmarketos.org"
+license="MIT"
+arch="armv7"
+options="!check !archcheck"
+depends="
+	linux-amazon-austin
+	mesa-dri-gallium
+	mkbootimg
+	postmarketos-base
+	msm-fb-refresher
+"
+makedepends="devicepkg-dev"
+source="deviceinfo"
+
+build() {
+	devicepkg_build $startdir $pkgname
+}
+
+package() {
+	devicepkg_package $startdir $pkgname
+}
+
+sha512sums="
+7996497bcd36f7c49ffc83392bc7528f9c8e911356e8eb890d537be2fd3bbef13a678b53b8f57a955503b128a0182db3ed5c95182c616a317d2e43ad6e603640  deviceinfo
+"