FocalTech touch controller

The focaltech controller is connected to host processor
via i2c. The controller generates interrupts when the
user touches the panel. The host controller is expected
to read the touch coordinates over i2c and pass the coordinates
to the rest of the system.

Required properties:

 - compatible		: should be "focaltech,fts".
 - reg				: i2c slave address of the device.
 - interrupt-parent	: parent of interrupt.
 - interrupts		: touch sample interrupt to indicate presense or release
				of fingers on the panel.
 - vdd-supply		: Power supply needed to power up the device.
 - vcc-i2c-supply	: Power source required to power up i2c bus.
 - focaltech,irq-gpio	: irq gpio which is to provide interrupts to host,
				same as "interrupts" node. It will also
				contain active low or active high information.
 - focaltech,reset-gpio	: reset gpio to control the reset of chip.
 - focaltech,display-coords : display coordinates in pixels. It is a four
				tuple consisting of min x, min y, max x and
				max y values

Optional properties:
 - focaltech,max-touch-number	: maximnum number of touch points supported.
 - focaltech,have-key 		: specify whether virtual keys are present.
 - focaltech,key-number 	: number of keys, maximum 3.
 - focaltech,keys 			: array of key code.
 - focaltech,key-y-coord 	: y coordinate for the keys.
 - focaltech,key-x-coords	: array of x coordinates for the keys.
 - focaltech,wakeup-gestures-en	: enable wakeup gestures.

Example:
	i2c@f9923000{
		focaltech@38{
			compatible = "focaltech,fts";
			reg = <0x38>;
			interrupt-parent = <&msmgpio>;
			interrupts = <98 0x2008>;
			vdd-supply = <&pm8110_l19>;
			vcc_i2c-supply = <&pm8110_l14>;
			focaltech,reset-gpio = <&msmgpio 16 0x00>;
			focaltech,irq-gpio = <&msmgpio 98 0x2008>;
			focaltech,display-coords = <0 0 480 800>;
			focaltech,max-touch-number = <2>;
			focaltech,have-key;
			focaltech,key-number = <3>;
			focaltech,keys = <139 142 140>;
			focaltech,key-y-coord = <700>;
			focaltech,key-x-coords = <80 240 400>;
		};
	};