dt-bindings: arm: atmel: add new sam9x60 SFR binding

Add this SFR compatible definition for the sam9x60 SoC. Will be needed
in OHCI driver: ohci-at91.c.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>