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>

Documentation/devicetree/bindings/arm/atmel-sysregs.txt

@@ -147,6 +147,7 @@ required properties:
 - compatible: Should be "atmel,<chip>-sfr", "syscon" or
 	"atmel,<chip>-sfrbu", "syscon"
   <chip> can be "sama5d3", "sama5d4" or "sama5d2".
+  It also can be "microchip,sam9x60-sfr", "syscon".
 - reg: Should contain registers location and length
 
 	sfr@f0038000 {