devicetree: bindings: gpio-davinic: fix documentation

This patch adds missing #gpio-cells and also adds a
usage example for leds.
Reported-by: NAlexander Holler <holler@ahsoftware.de>
Signed-off-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/gpio-davinci.txt

@@ -8,6 +8,10 @@ Required Properties:
 
 - gpio-controller : Marks the device node as a gpio controller.
 
+- #gpio-cells : Should be two.
+  - first cell is the pin number
+  - second cell is used to specify optional parameters (unused)
+
 - interrupt-parent: phandle of the parent interrupt controller.
 
 - interrupts: Array of GPIO interrupt number. Only banked or unbanked IRQs are
@@ -27,6 +31,7 @@ Example:
 gpio: gpio@1e26000 {
 	compatible = "ti,dm6441-gpio";
 	gpio-controller;
+	#gpio-cells = <2>;
 	reg = <0x226000 0x1000>;
 	interrupt-parent = <&intc>;
 	interrupts = <42 IRQ_TYPE_EDGE_BOTH 43 IRQ_TYPE_EDGE_BOTH
@@ -39,3 +44,19 @@ gpio: gpio@1e26000 {
 	interrupt-controller;
 	#interrupt-cells = <2>;
 };
+
+leds {
+	compatible = "gpio-leds";
+
+	led1 {
+		label = "davinci:green:usr1";
+		gpios = <&gpio 10 GPIO_ACTIVE_HIGH>;
+		...
+	};
+
+	led2 {
+		label = "davinci:red:debug1";
+		gpios = <&gpio 11 GPIO_ACTIVE_HIGH>;
+		...
+	};
+};