dt-bindings: add bindings for SAM9X60

Add device tree binding for SAM9X60 pin controller.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/atmel,at91-pinctrl.txt

@@ -19,7 +19,7 @@ such as pull-up, multi drive, etc.
 
 Required properties for iomux controller:
 - compatible: "atmel,at91rm9200-pinctrl" or "atmel,at91sam9x5-pinctrl"
-		or "atmel,sama5d3-pinctrl"
+		or "atmel,sama5d3-pinctrl" or "microchip,sam9x60-pinctrl"
 - atmel,mux-mask: array of mask (periph per bank) to describe if a pin can be
   configured in this periph mode. All the periph and bank need to be describe.
 
@@ -117,7 +117,8 @@ Some requirements for using atmel,at91rm9200-pinctrl binding:
 4. The gpio controller must be describe in the pinctrl simple-bus.
 
 For each bank the required properties are:
-- compatible: "atmel,at91sam9x5-gpio" or "atmel,at91rm9200-gpio"
+- compatible: "atmel,at91sam9x5-gpio" or "atmel,at91rm9200-gpio" or
+  "microchip,sam9x60-gpio"
 - reg: physical base address and length of the controller's registers
 - interrupts: interrupt outputs from the controller
 - interrupt-controller: marks the device node as an interrupt controller