sunxi: Add defconfig and dts file for Polaroid MID2407PXE03 tablet

The Polaroid MID2407PXE03 is an a23 based 7" tablet based on a M86_MB V2.0
PCB, featuring a 800x480 LCD, 512MB RAM, 4G NAND, esp8089 wifi, gsl1680
touchschreen, micro-sd slot, 3.5mm headphone jack and a micro-usb otg
connector which doubles as charging port.

The dts file is identical to the one submitted to the upstream kernel.

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