ARM: dts: imx: update #interrupt-cells for gpio nodes

Change the value of #interrupt-cells of gpio nodes from 1 to 2, so that
the gpio irq type can be specified in device tree.  Also update binding
document to make it clear.

Reported-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt b/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt
index 5f360e7..4f39297 100644
--- a/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt
@@ -11,6 +11,13 @@
   the second cell is used to specify the gpio polarity:
       0 = active high
       1 = active low
+- interrupt-controller: Marks the device node as an interrupt controller.
+- #interrupt-cells : Should be 2.  The first cell is the GPIO number.
+  The second cell bits[3:0] is used to specify trigger type and level flags:
+      1 = low-to-high edge triggered.
+      2 = high-to-low edge triggered.
+      4 = active high level-sensitive.
+      8 = active low level-sensitive.
 
 Example:
 
@@ -20,4 +27,6 @@
 	interrupts = <50 51>;
 	gpio-controller;
 	#gpio-cells = <2>;
+	interrupt-controller;
+	#interrupt-cells = <2>;
 };