gpio/tegra: add devicetree support

Add support for decoding gpios from the device tree
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NOlof Johansson <olof@lixom.net>

Documentation/devicetree/bindings/gpio/gpio_nvidia.txt

+NVIDIA Tegra 2 GPIO controller
+
+Required properties:
+- compatible : "nvidia,tegra250-gpio"
+- #gpio-cells : Should be two. The first cell is the pin number and the
+  second cell is used to specify optional parameters (currently unused).
+- gpio-controller : Marks the device node as a GPIO controller.

drivers/gpio/gpio-tegra.c

@@ -23,6 +23,7 @@
 
 #include <linux/io.h>
 #include <linux/gpio.h>
+#include <linux/of.h>
 
 #include <asm/mach/irq.h>
 
@@ -340,6 +341,15 @@ static int __init tegra_gpio_init(void)
 		}
 	}
 
+#ifdef CONFIG_OF_GPIO
+	/*
+	 * This isn't ideal, but it gets things hooked up until this
+	 * driver is converted into a platform_device
+	 */
+	tegra_gpio_chip.of_node = of_find_compatible_node(NULL, NULL,
+						"nvidia,tegra250-gpio");
+#endif /* CONFIG_OF_GPIO */
+
 	gpiochip_add(&tegra_gpio_chip);
 
 	for (i = INT_GPIO_BASE; i < (INT_GPIO_BASE + TEGRA_NR_GPIOS); i++) {