ARM: at91: Add support for board aks-cdu

Add support for our "aks-cdu" board based up on Telit's module GE863 Pro3.
It has more uarts, leds, another nand partitioning.

Signed-off-by: Jiri Prchal <jiri.prchal@aksignal.cz>
[nicolas.ferre@atmel.com: correction of the dts file]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>