NXP LPC32xx Key Scan Interface

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.
- keypad,num-rows: Number of rows and columns, e.g. 1: 1x1, 6: 6x6
- keypad,num-columns: Must be equal to keypad,num-rows since LPC32xx only
  supports square matrices
- 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

Example:

	key@40050000 {
		compatible = "nxp,lpc3220-key";
		reg = <0x40050000 0x1000>;
		interrupts = <54 0>;
		keypad,num-rows = <1>;
		keypad,num-columns = <1>;
		nxp,debounce-delay-ms = <3>;
		nxp,scan-delay-ms = <34>;
		linux,keymap = <0x00000002>;
	};