ARM: dts: sun4i: Add initial dts for Gemei G9 tablet

Gemei G9 is an A10 based tablet, with 1G RAM, 16G NAND, 1024x768
IPS LCD display, stereo speakers, 1.3MP front camera and 5 MP
rear camera, 8000mAh battery, GT901 2+1 touchscreen, Bosch BMA250
accelerometer and RTL8188CUS USB wifi. It also has MicroSD slot,
miniHDMI, 1 x MicroUSB OTG port and 1 x MicroUSB host port and
3.5mm headphone jack.

Changes since v2:
 * Fix syntax error (brown paper bag release)

Changes since v1:
 * Added sun4i-lradc keymap
 * Added TODO note about missing IRQ pins for bma250
 * Fixed formatting issues and removed external URLs

Signed-off-by: Priit Laes <plaes@plaes.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>