ps8622-bridge bindings

Required properties:
	- compatible: "parade,ps8622" or "parade,ps8625"
	- reg: first i2c address of the bridge
	- sleep-gpios: OF device-tree gpio specification for PD_ pin.
	- reset-gpios: OF device-tree gpio specification for RST_ pin.
	- parade,regs: List of 3-byte registers tuples to write:
		<I2C chip address offset> <register> <value>

Optional properties:
	- lane-count: number of DP lanes to use
	- use-external-pwm: backlight will be controlled by an external PWM
	- video interfaces: Device node can contain video interface port
			    nodes for panel according to [1].

[1]: Documentation/devicetree/bindings/media/video-interfaces.txt

Example:
	lvds-bridge@48 {
		compatible = "parade,ps8622";
		reg = <0x48>;
		sleep-gpios = <&gpc3 6 1 0 0>;
		reset-gpios = <&gpc3 1 1 0 0>;
		lane-count = <1>;
		ports {
			port@0 {
				bridge_out: endpoint {
					remote-endpoint = <&panel_in>;
				};
			};
		};
	};