ARM: dts: sun5i: Add dts file for q8 formfactor a13 based tablets

This commits adds a generic dts file for q8 formfactor a13 based tablets.

The tablets ship in many variants, with the difference mainly being the
touchscreen controller / accelerometer / wifi chip used.

The wifi is USB based, and thus not listed in devicetree.

The touchscreen controller / accelerometer may turn out to be a problem
once we add support for those. We can either do something with devicetree
overlays, or add sun5i-a13-<touchscreen>-<accelerometer>.dts files. The
latter is what the android mod community is doing with firmware images.

This dts was tested with an a13 q8 tablet with a pcb labelled: "94V-0",
silead gsl1680 touchscreen controller and a mc32x0 accelerometer.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>