ARM: sun7i: dt: Add new MK808C device

The MK808C is an A20 based android stick, with 1G RAM, 8G NAND flash,
a RTL8723au wifi + bt combo chip, a USB host ports using USB-A receptacles,
a mini USB-B receptacle for USB OTG, mini HDMI and a TRS connector for AV.

This patch adds basic support for the device, more information can be found
here (http://linux-sunxi.org/MK808C

).

Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>