sunxi: Hookup OTG USB controller support

Hookup OTG USB controller support and enable the otg controller + USB-keyb
on various tablets.

This allows tablet owners to interact with u-boot without needing to solder
a serial console onto their tablet PCB.

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