[ARM] 5130/4: Support for the at91sam9g20

Support for the at91sam9g20 : Atmel 400Mhz ARM 926ej-s SOC.

AT91sam9g20 is an evolution of the at91sam9260 with a faster clock
speed.
We created a new board for this device but based the chip support
directly on 9260 files with little updates.
Here is the chip page on Atmel wabsite:
http://atmel.com/dyn/products/product_card.asp?part_id=4337

Signed-off-by: Sedji Gaouaou <sedji.gaouaou@atmel.com>
Signed-off-by: Justin Waters <justin.waters@timesys.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>