ARM: dts: sun8i: Add dts file for inet-d978_rev2 tablets

The inet-d978_rev2 is a pcb used in generic A33 based tablets. It features
volume buttons, micro-usb otg, headphone connector and a power button.

On the board a Realtek RTL8723BS SDIO Wi-Fi module are soldered, and there
is also a accompanied board which has a Goodix GT9271 soldered.

As this board is desired to create tablets with a Home key dealed by
GT9271, a LED is present at the front panel at the position of the
Home key.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>