QTI Snapdragon Display Engine (SDE) shared display

Required properties:
- compatible:		"qcom,shared-display"
- qcom,shared-display-base: node handle of qcom,shared-display-base, see below.
- qcom,blend-stage-range: blend stage range that are not shared in one display
- qcom,shared-display-src-mode: source resolution of the shared display, contains
			two properties:
			qcom,mode-h-active: horizontal resolution
			qcom,mode-v-active: vertical resolution
- qcom,shared-display-dst-mode: destination rectangle in the shared display,
			contains 4 properties:
			qcom,mode-x-offset: x offset inside the shared display
			qcom,mode-y-offset: y offset inside the shared display
			qcom,mode-width: width inside the shared display
			qcom,mode-height: height inside the shared display


qcom,shared-display-base properties:
- qcom,shared-display-base-intf: intf index of the base display
- qcom,shared-display-base-mst: if display is DP MST type, optional
- qcom,shared-display-base-mode: timing of the base display, contains the
			following properties:
			qcom,mode-h-active: H active size
			qcom,mode-h-front-porch: H front portch
			qcom,mode-h-pulse-width: H pulse width
			qcom,mode-h-back-porch: H back porch
			qcom,mode-h-active-high: if H active polarity is high
			qcom,mode-v-active: V active size
			qcom,mode-v-front-porch: V front portch
			qcom,mode-v-pulse-width: V pulse width
			qcom,mode-v-back-porch: V back porch
			qcom,mode-v-active-high: if V active polarity is high
			qcom,mode-refresh-rate: vertial refresh rate
			qcom,mode-clock-in-khz: clock in kHz

Example:

/ {
	...

	sde_sh_base0: qcom,shared-display-base@0 {
		qcom,shared-display-base-intf = <0>;
		qcom,shared-display-base-mst;
		qcom,shared-display-base-mode {
			qcom,mode-h-active = <3840>;
			qcom,mode-h-front-porch = <176>;
			qcom,mode-h-pulse-width = <88>;
			qcom,mode-h-back-porch = <296>;
			qcom,mode-h-active-high;
			qcom,mode-v-active = <2160>;
			qcom,mode-v-front-porch = <8>;
			qcom,mode-v-pulse-width = <10>;
			qcom,mode-v-back-porch = <72>;
			qcom,mode-v-active-high;
			qcom,mode-refresh-rate = <30>;
			qcom,mode-clock-in-khz = <297000>;
		};
	};

	sde_sh0: qcom,shared-display@0 {
		compatible = "qcom,shared-display";
		qcom,shared-display-base = <&sde_sh_base0>;
		qcom,blend-stage-range = <0 5>;
		qcom,shared-display-src-mode {
			qcom,mode-h-active = <1920>;
			qcom,mode-v-active = <1080>;
		};
		qcom,shared-display-dst-mode {
			qcom,mode-x-offset = <0>;
			qcom,mode-y-offset = <0>;
			qcom,mode-width = <1920>;
			qcom,mode-height = <1080>;
		};
	};

};
