Bindings for EETI touchscreen controller

Required properties:
- compatible:	should be "eeti,exc3000-i2c"
- reg:		I2C address of the chip. Should be set to <0xa>
- interrupts:	interrupt to which the chip is connected

Optional properties:
- attn-gpios:	A handle to a GPIO to check whether interrupt is still
		latched. This is necessary for platforms that lack
		support for level-triggered IRQs.

The following optional properties described in touchscreen.txt are
also supported:

- touchscreen-inverted-x
- touchscreen-inverted-y
- touchscreen-swapped-x-y

Example:

i2c-master {
	touchscreen@a {
		compatible = "eeti,exc3000-i2c";
		reg = <0xa>;
		interrupt-parent = <&gpio>;
		interrupts = <123 IRQ_TYPE_EDGE_RISING>;
		attn-gpios = <&gpio 123 GPIO_ACTIVE_HIGH>;
	};
};