samsung-xcover4lte: new device

This MR adds support for the Samsung Galaxy Xcover 4 (codename: xcover4lte).

works:

• USB (and USB networking)
• Display
• Touchscreen
• Xorg
• Charging
• WiFi

doesn't work:

• Wayland
• Audio
• Camera (uses fimc-is2, causes kernel to panic when running udev)

note: WiFi needs device-specific firmware files (mx: empty file, mx140.bin: firmware?, mx140_wlan.hcf: config??). They don't seem to be available on GitHub/GitLab/etc. (files with the same name are available, one repo seems to have the exact same "mx140.bin" file but doesn't have the same "mx140_wlan.hcf" file). I'm not sure how (and where) these files should be backed up.

wiki page: https://wiki.postmarketos.org/wiki/Samsung_Galaxy_Xcover_4_(samsung-xcover4lte)

device/testing/device-samsung-xcover4lte/APKBUILD

+# Reference: <https://postmarketos.org/devicepkg>
+pkgname=device-samsung-xcover4lte
+pkgdesc="Samsung Galaxy Xcover 4"
+pkgver=0.1
+pkgrel=0
+url="https://postmarketos.org"
+license="MIT"
+arch="aarch64"
+options="!check !archcheck"
+depends="postmarketos-base linux-samsung-xcover4lte mkbootimg mesa-dri-gallium msm-fb-refresher"
+makedepends="devicepkg-dev"
+source="deviceinfo"
+
+build() {
+	devicepkg_build $startdir $pkgname
+}
+
+package() {
+	devicepkg_package $startdir $pkgname
+}
+
+sha512sums="
+79b5e23e53e5a2fcfba3f4399bb30d8db71d890810c5cbe08054f6e6e8f1068ba2ea6e42251a51daf678a416566634b17afc8abac1a1aa23795ffdd7841db6f3  deviceinfo
+"