Elan Ektf3xx series touch controller

   Required properties:

		- compatible				: Should be "elan,ekth3500"
		- reg				        : I2C slave address of the device.
		- interrupt-parent			: Parent of interrupt.
		- interrupts				: Configuration of touch panel controller interrupt GPIO.
		- elan,irq-gpio				: Interrupt gpio which is to provide interrupts to
										host, same as "interrupts" node.It will also contain
										active low or active high information

  Optional properties:

		- vdd-supply				: Power supply needed to power up the device, when use
										external regulator, do not add this property.
		- vccio-supply				: Power source required to power up i2c bus.
										Ekth3500 series can provide 1.8V from internal
										LDO, add this properties base on hardware design.
		- reset-gpio			    : Reset gpio to control the reset of chip.

  Example:
		i2c@f9923000{
			elan_ktf@10 {
				compatible = "elan,ekth3500";
				reg = <0x10>;
				vdd-supply = <&pm8110_l19>;
				vccio-supply = <&pm8110_l14>;
				reset-gpio = <&msmgpio 0 GPIO_ACTIVE_LOW>;
				interrupt-parent = <&msmgpio>;
				interrupts = <1 0x2>;
				elan,irq-gpio = <&tlmm 65 0x2008>;>
			};
		};
