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

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

Optional properties:
- st,sample-time: ADC converstion time in number of clock.  (0 -> 36 clocks, 1 ->
  44 clocks, 2 -> 56 clocks, 3 -> 64 clocks, 4 -> 80 clocks, 5 -> 96 clocks, 6
  -> 144 clocks), recommended is 4.
- st,mod-12b: ADC Bit mode (0 -> 10bit ADC, 1 -> 12bit ADC)
- st,ref-sel: ADC reference source (0 -> internal reference, 1 -> external
  reference)
- 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 (0 -> 10 us, 1 -> 50 us, 2 ->
  100 us, 3 -> 500 us, 4-> 1 ms, 5 -> 5 ms, 6 -> 10 ms, 7 -> 50 ms) recommended
  is 3
- st,settling: Panel driver settling time (0 -> 10 us, 1 -> 100 us, 2 -> 500 us, 3
  -> 1 ms, 4 -> 5 ms, 5 -> 10 ms, 6 for 50 ms, 7 -> 100 ms) recommended is 2
- st,fraction-z: Length of the fractional part in z (fraction-z ([0..7]) = Count of
  the fractional part) recommended is 7
- st,i-drive: current limit value of the touchscreen drivers (0 -> 20 mA typical 35
  mA 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>;
	};