Atmel maXTouch touchscreen/touchpad

Required properties:
- compatible:
    atmel,maxtouch

- reg: The I2C address of the device

- interrupts: The sink for the touchpad's IRQ output
    See ../interrupt-controller/interrupts.txt

Optional properties for main touchpad device:

- linux,gpio-keymap: When enabled, the SPT_GPIOPWN_T19 object sends messages
    on GPIO bit changes. An array of up to 8 entries can be provided
    indicating the Linux keycode mapped to each bit of the status byte,
    starting at the LSB. Linux keycodes are defined in
    <dt-bindings/input/input.h>.

    Note: the numbering of the GPIOs and the bit they start at varies between
    maXTouch devices. You must either refer to the documentation, or
    experiment to determine which bit corresponds to which input. Use
    KEY_RESERVED for unused padding values.

- atmel,suspend-mode: Select method used to suspend:
    MXT_SUSPEND_DEEP_SLEEP - use T7 to suspend the device into deep sleep
    MXT_SUSPEND_T9_CTRL - use T9.CTRL to turn off touch processing
    Definitions are in <dt-bindings/input/atmel_mxt_ts.h>.

- atmel,reset-gpio: Configure RESET GPIO. Required for regulator support.

- atmel,cfg_name: Provide name of configuration file in OBP_RAW format. This
    will be downloaded from the firmware loader on probe to the device.

- atmel,input_name: Override name of input device from the default.

Example:

	touch@4b {
		compatible = "atmel,maxtouch";
		reg = <0x4b>;
		interrupt-parent = <&gpio>;
		interrupts = <TEGRA_GPIO(W, 3) IRQ_TYPE_LEVEL_LOW>;
	};