USB: at91: Device udc add dt support

Allow to compile it if AT91 is enable.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/atmel-usb.txt

@@ -29,3 +29,21 @@ usb1: ehci@00800000 {
 	reg = <0x00800000 0x100000>;
 	interrupts = <22 4>;
 };
+
+AT91 USB device controller
+
+Required properties:
+ - compatible: Should be "atmel,at91rm9200-udc"
+ - reg: Address and length of the register set for the device
+ - interrupts: Should contain macb interrupt
+
+Optional properties:
+ - atmel,vbus-gpio: If present, specifies a gpio that needs to be
+   activated for the bus to be powered.
+
+usb1: gadget@fffa4000 {
+	compatible = "atmel,at91rm9200-udc";
+	reg = <0xfffa4000 0x4000>;
+	interrupts = <10 4>;
+	atmel,vbus-gpio = <&pioC 5 0>;
+};