ARM: dts: pxa: fix no. of gpio cells in the pxa gpio binding documentation

Fix the no. of gpio cells in pxa gpio binding documentation.

The no. of gpio cells for the pxa gpio is actually 2. But is
incorrectly specified as 1, in the binding documentation. From the
driver code, the second cell specifies the standard flags as described
in gpio.txt.
Signed-off-by: Vijay Kumar B. <vijaykumar@zilogic.com>
[fixed subject line]
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>

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

@@ -17,7 +17,9 @@ Required properties:
 - #interrupt-cells: Specifies the number of cells needed to encode an
   interrupt source.
 - gpio-controller : Marks the device node as a gpio controller.
-- #gpio-cells : Should be one.  It is the pin number.
+- #gpio-cells : Should be two.  The first cell is the pin number and
+  the second cell is used to specify flags. See gpio.txt for possible
+  values.
 
 Example for a MMP platform:
 
@@ -27,7 +29,7 @@ Example for a MMP platform:
 		interrupts = <49>;
 		interrupt-names = "gpio_mux";
 		gpio-controller;
-		#gpio-cells = <1>;
+		#gpio-cells = <2>;
 		interrupt-controller;
 		#interrupt-cells = <1>;
       };