Synaptics RMI4 2D Sensor Device Binding

The Synaptics RMI4 core is able to support RMI4 devices using different
transports and different functions. This file describes the device tree
bindings for devices which contain 2D sensors using Function 11 or
Function 12. Complete documentation for transports and other functions
can be found in:
Documentation/devicetree/bindings/input/rmi4.

RMI4 Function 11 and Function 12 are for 2D touch position sensing.
Additional documentation for F11 can be found at:
http://www.synaptics.com/sites/default/files/511-000136-01-Rev-E-RMI4-Interfacing-Guide.pdf

Optional Touch Properties:
Description in Documentation/devicetree/bindings/input/touch
- touchscreen-inverted-x
- touchscreen-inverted-y
- touchscreen-swapped-x-y
- touchscreen-x-mm
- touchscreen-y-mm

Optional Properties:
- syna,clip-x-low: Sets a minimum value for X.
- syna,clip-y-low: Sets a minimum value for Y.
- syna,clip-x-high: Sets a maximum value for X.
- syna,clip-y-high: Sets a maximum value for Y.
- syna,offset-x: Add an offset to X.
- syna,offset-y: Add an offset to Y.
- syna,delta-x-threshold: Set the minimum distance on the X axis required
				to generate an interrupt in reduced reporting
				mode.
- syna,delta-y-threshold: Set the minimum distance on the Y axis required
				to generate an interrupt in reduced reporting
				mode.
- syna,sensor-type: Set the sensor type. 1 for touchscreen 2 for touchpad.
- syna,disable-report-mask: Mask for disabling posiiton reporting. Used to
				disable reporing absolute position data.
- syna,rezero-wait-ms: Time in miliseconds to wait after issuing a rezero
				command.


Example of a RMI4 I2C device with F11:
Example:
	&i2c1 {
		rmi4-i2c-dev@2c {
			compatible = "syna,rmi4-i2c";

			...

			rmi4-f11@11 {
				reg = <0x11>;
				touchscreen-inverted-y;
				syna,sensor-type = <2>;
			};
		};
	};