Input: lpc32xx-key - add clocks property and fix DT binding example

The keypad controller on NXP LPC32xx requires its clock gate to be open,
therefore add description of the requires 'clocks' property.

In addition adjust the example by adding description of required 'clocks'
property and by fixing 'interrupts' property.
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/lpc32xx-key.txt

@@ -8,6 +8,7 @@ Required Properties:
 - reg: Physical base address of the controller and length of memory mapped
   region.
 - interrupts: The interrupt number to the cpu.
+- clocks: phandle to clock controller plus clock-specifier pair
 - nxp,debounce-delay-ms: Debounce delay in ms
 - nxp,scan-delay-ms: Repeated scan period in ms
 - linux,keymap: the key-code to be reported when the key is pressed
@@ -22,7 +23,9 @@ Example:
 	key@40050000 {
 		compatible = "nxp,lpc3220-key";
 		reg = <0x40050000 0x1000>;
-		interrupts = <54 0>;
+		clocks = <&clk LPC32XX_CLK_KEY>;
+		interrupt-parent = <&sic1>;
+		interrupts = <22 IRQ_TYPE_LEVEL_HIGH>;
 		keypad,num-rows = <1>;
 		keypad,num-columns = <1>;
 		nxp,debounce-delay-ms = <3>;