ARM: at91: dt: at91sam9g45 family and board device tree files

Create a new device tree source file for Atmel at91sam9g45 SoC family.
The Evaluation Kit at91sam9m10g45ek includes it.
This first basic support will be populated as drivers and boards will be
converted to device tree.
Contains serial, dma and interrupt controllers.

The generic board file still takes advantage of platform data for early serial
init. As we need a storage media and the NAND flash driver is not converted to
DT yet, we keep old initialization for it.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reviewed-by: Rob Herring <rob.herring@calxeda.com>