sunxi: Add support for gt90h-v4 tablets

sunxi: Add support for gt90h-v4 tablets

The gt90h is a pcb found in generic 9" tablets with an A23 soc, 1G RAM
and 8G nand, rtl8723as usb wifi, 1 micro usb port and 1 micro sd slot.

The pmic setup on this board is somewhat special, dcdc2 MUST be set
to 1.1V instead of the usual 1.2V otherwise the board is very unstable.
aldo1 is used to power the micro sd slot, dldo1 is used for wifi.

This commit adds a defconfig + dts (as submitted to the kernel) for
the gt90h-v4 pcb.

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