STMPE Touchscreen
----------------

Required properties:
 - compatible: "st,stmpe-ts"

Optional properties:
- st,sample-time	: ADC conversion time in number of clock.
				0 -> 36 clocks
				1 -> 44 clocks
				2 -> 56 clocks
				3 -> 64 clocks
				4 -> 80 clocks (recommended)
				5 -> 96 clocks
				6 -> 144 clocks
- st,mod-12b		: ADC Bit mode
				0 -> 10bit ADC
				1 -> 12bit ADC
- st,ref-sel		: ADC reference source
				0 -> internal
				1 -> external
- st,adc-freq		: ADC Clock speed
				0 -> 1.625 MHz
				1 -> 3.25 MHz
				2 || 3 -> 6.5 MHz
- st,ave-ctrl		: Sample average control
				0 -> 1 sample
				1 -> 2 samples
				2 -> 4 samples
				3 -> 8 samples
- st,touch-det-delay	: Touch detect interrupt delay (recommended is 3)
				0 -> 10 us
				1 -> 50 us
				2 -> 100 us
				3 -> 500 us
				4 -> 1 ms
				5 -> 5 ms
				6 -> 10 ms
				7 -> 50 ms
- st,settling		: Panel driver settling time (recommended is 2)
				0 -> 10 us
				1 -> 100 us
				2 -> 500 us
				3 -> 1 ms
				4 -> 5 ms
				5 -> 10 ms
				6 -> 50 ms
				7 -> 100 ms
- st,fraction-z		: Length of the fractional part in z (recommended is 7)
			  (fraction-z ([0..7]) = Count of the fractional part)
- st,i-drive		: current limit value of the touchscreen drivers
				0 -> 20 mA (typical 35mA max)
				1 -> 50 mA (typical 80 mA max)

Node name must be stmpe_touchscreen and should be child node of stmpe node to
which it belongs.

Example:

	stmpe_touchscreen {
		compatible = "st,stmpe-ts";
		st,sample-time = <4>;
		st,mod-12b = <1>;
		st,ref-sel = <0>;
		st,adc-freq = <1>;
		st,ave-ctrl = <1>;
		st,touch-det-delay = <2>;
		st,settling = <2>;
		st,fraction-z = <7>;
		st,i-drive = <1>;
	};