sunxi: add support for Beelink X2

sunxi: add support for Beelink X2

Specifications:
- SoC: Allwinner H3 Quad Cortex-A7 1.2GHz
- Flash: 8GB eMMC
- RAM: 1GB DDR3
- Ethernet: 1x100M
- Wifi: RTL8189FTV or AP6181
- 1x USB-A Host
- 1x USB-A Host/Device
- 2x Button
- 2x LED
- HDMI, SPDIF, IR

Install by following standard SD card flashing instructions.
Image can also be flashed to eMMC.

Signed-off-by: Kyle Hendry <kylehendrydev@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/18732
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>