ARM: at91: dt: sam9261: Device Tree support for the at91sam9261ek

ARM: at91: dt: sam9261: Device Tree support for the at91sam9261ek

This patch implements a DTS to boot a at91sam9261ek with a dt-enabled
kernel (at91_dt_defconfig).
supported features are:
* dbgu
* lcdc
* usb host
* usb gadget,
* spi dataflash
* nand flash
* touchscreen
* leds
* user buttons

In the TODO list:
* dm9000 (ethernet)
* audio
* mmc

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>