Pervasive Displays RePaper branded e-ink displays

Required properties:
- compatible:		"pervasive,e1144cs021" for 1.44" display
			"pervasive,e1190cs021" for 1.9" display
			"pervasive,e2200cs021" for 2.0" display
			"pervasive,e2271cs021" for 2.7" display

- panel-on-gpios:	Timing controller power control
- discharge-gpios:	Discharge control
- reset-gpios:		RESET pin
- busy-gpios:		BUSY pin

Required property for e2271cs021:
- border-gpios:		Border control

The node for this driver must be a child node of a SPI controller, hence
all mandatory properties described in ../spi/spi-bus.txt must be specified.

Optional property:
- pervasive,thermal-zone:	name of thermometer's thermal zone

Example:

	display_temp: lm75@48 {
		compatible = "lm75b";
		reg = <0x48>;
		#thermal-sensor-cells = <0>;
	};

	thermal-zones {
		display {
			polling-delay-passive = <0>;
			polling-delay = <0>;
			thermal-sensors = <&display_temp>;
		};
	};

	papirus27@0{
		compatible = "pervasive,e2271cs021";
		reg = <0>;

		spi-max-frequency = <8000000>;

		panel-on-gpios = <&gpio 23 0>;
		border-gpios = <&gpio 14 0>;
		discharge-gpios = <&gpio 15 0>;
		reset-gpios = <&gpio 24 0>;
		busy-gpios = <&gpio 25 0>;

		pervasive,thermal-zone = "display";
	};