sunxi: Add Hyundai A7HD support

The Hyundai A7HD is a 7" 16:9 A10 powered tablet featuring 1G RAM, 8G
nand, 1024x600 IPS screen, a mini hdmi port, mini usb receptacle and a
headphones port for details see: http://linux-sunxi.org/Hyundai_A7HD



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