NXP LPC32xx Key Scan Interface

This binding is based on the matrix-keymap binding with the following
changes:

Required Properties:
- compatible: Should be "nxp,lpc3220-key"
- 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
  and released, see also
  Documentation/devicetree/bindings/input/matrix-keymap.txt

Note: keypad,num-rows and keypad,num-columns are required, and must be equal
since LPC32xx only supports square matrices

Example:

	key@40050000 {
		compatible = "nxp,lpc3220-key";
		reg = <0x40050000 0x1000>;
		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>;
		nxp,scan-delay-ms = <34>;
		linux,keymap = <0x00000002>;
	};
