Required properties:
- compatible: "brcm,bcm2835-gpio"
-- reg: Should contain the physical address of the GPIO module's registes.
+- reg: Should contain the physical address of the GPIO module's registers.
- gpio-controller: Marks the device node as a GPIO controller.
- #gpio-cells : Should be two. The first cell is the pin number and the
second cell is used to specify optional parameters: