* Tegra keyboard controller
The key controller has maximum 24 pins to make matrix keypad. Any pin
can be configured as row or column. The maximum column pin can be 8
and maximum row pins can be 16 for Tegra20/Tegra30.

Required properties:
- compatible: "nvidia,tegra20-kbc"
- reg: Register base address of KBC.
- interrupts: Interrupt number for the KBC.
- nvidia,kbc-row-pins: The KBC pins which are configured as row. This is an
  array of pin numbers which is used as rows.
- nvidia,kbc-col-pins: The KBC pins which are configured as column. This is an
  array of pin numbers which is used as column.
- linux,keymap: The keymap for keys as described in the binding document
  devicetree/bindings/input/matrix-keymap.txt.
- clocks: Must contain one entry, for the module clock.
  See ../clocks/clock-bindings.txt for details.
- resets: Must contain an entry for each entry in reset-names.
  See ../reset/reset.txt for details.
- reset-names: Must include the following entries:
  - kbc

Optional properties, in addition to those specified by the shared
matrix-keyboard bindings:

- linux,fn-keymap: a second keymap, same specification as the
  matrix-keyboard-controller spec but to be used when the KEY_FN modifier
  key is pressed.
- nvidia,debounce-delay-ms: delay in milliseconds per row scan for debouncing
- nvidia,repeat-delay-ms: delay in milliseconds before repeat starts
- nvidia,ghost-filter: enable ghost filtering for this device
- nvidia,wakeup-source: configure keyboard as a wakeup source for suspend/resume

Example:

keyboard: keyboard {
	compatible = "nvidia,tegra20-kbc";
	reg = <0x7000e200 0x100>;
	interrupts = <0 85 0x04>;
	clocks = <&tegra_car 36>;
	resets = <&tegra_car 36>;
	reset-names = "kbc";
	nvidia,ghost-filter;
	nvidia,debounce-delay-ms = <640>;
	nvidia,kbc-row-pins = <0 1 2>;    /* pin 0, 1, 2 as rows */
	nvidia,kbc-col-pins = <11 12 13>; /* pin 11, 12, 13 as columns */
	linux,keymap = <0x00000074
			0x00010067
			0x00020066
			0x01010068
			0x02000069
			0x02010070
			0x02020071>;
};
