sunxi: Add support for Cubieboard4

The Cubieboard4 is an A80 SoC based development board from Cubietech.

This board has a UART port, 4 USB host ports, a USB 3.0 OTG connector,
HDMI and VGA outputs, a micro SD slot, 8G eMMC flash, 2G DRAM, a WiFi/BT
combo chip, headphone and microphone jacks, IR receiver, and GPIO headers.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>