* Freescale i.MX6UL Touch Controller

Required properties:
- compatible: must be "fsl,imx6ul-tsc".
- reg: this touch controller address and the ADC2 address.
- interrupts: the interrupt of this touch controller and ADC2.
- clocks: the root clock of touch controller and ADC2.
- clock-names; must be "tsc" and "adc".
- xnur-gpio: the X- gpio this controller connect to.
  This xnur-gpio returns to low once the finger leave the touch screen (The
  last touch event the touch controller capture).

Optional properties:
- measure-delay-time: the value of measure delay time.
  Before X-axis or Y-axis measurement, the screen need some time before
  even potential distribution ready.
  This value depends on the touch screen.
- pre-charge-time: the touch screen need some time to precharge.
  This value depends on the touch screen.
- touchscreen-average-samples: Number of data samples which are averaged for
  each read. Valid values are 1, 4, 8, 16 and 32.

Example:
	tsc: tsc@2040000 {
		compatible = "fsl,imx6ul-tsc";
		reg = <0x02040000 0x4000>, <0x0219c000 0x4000>;
		interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>,
			     <GIC_SPI 101 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&clks IMX6UL_CLK_IPG>,
			 <&clks IMX6UL_CLK_ADC2>;
		clock-names = "tsc", "adc";
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_tsc>;
		xnur-gpio = <&gpio1 3 GPIO_ACTIVE_LOW>;
		measure-delay-time = <0xfff>;
		pre-charge-time = <0xffff>;
		touchscreen-average-samples = <32>;
	};
