sunxi: Add mk802 board / defconfig

The mk802 is the "classic" Allwinner A10 based hdmi tv-stick, it features
512M or 1G RAM, 4G nand, a mini-hdmi female connector, USB-A receptacle,
mini-usb receptacle (OTG) and USB-wifi. Somewhat unique the mk802 does not
use the AXP209 pmic, it does not have a pmic at all.

For more details see: http://linux-sunxi.org/Rikomagic_mk802



Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>