sunxi: Add support for OrangePi Zero2

sunxi: Add support for OrangePi Zero2

OrangePi Zero2 is SBC based on Allwinner H616 with 1 GiB of RAM, SD card
support, gigabit ethernet, micro HDMI, WIFI, Bluetooth and 1 USB 2.0
port. It also has two GPIO headers which allows further peripherals to
be used.

The devicetree file is taken from v3 of the OrangePi Zero2 Linux
submission [1], which it's not yet merged.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2021-January/632084.html

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>