ARM: dts: mmp3: Add MMP3 SoC dts file

Describes most of the hardware found on Marvell MMP3, aka PXA2128, aka
Armada 620. Missing bits are the LCD controller, HSIC controllers,
Audio and GPU. Will be completed once bindings and drivers settle.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>