Qualcomm MDSS EDP

MDSS EDP is a edp driver which supports panels that are compatable with
VESA EDP display interface specification.

Required properties
- compatible :				Must be "qcom,mdss-edp".
- reg :						Offset and length of the register set for the
							device.
- reg-names :				Names to refer to register sets related to this
							device
- vdda-supply :				Phandle for vdd regulator device node.
- gpio-panel-en	:			GPIO for supplying power to panel and backlight
							driver.
- qcom,panel-lpg-channel :		LPG channel for backlight.
- qcom,panel-pwm-period :		PWM period in microseconds.
- status :				A string that has to be set to "okay/ok" to enable
						the driver. By default this property will be set to
						"disable". Will be set to "ok/okay" status for
						specific platforms.
- qcom,mdss-fb-map:			pHandle that specifies the framebuffer to which the
					interface is mapped.

Example:
	mdss_edp: qcom,mdss_edp@fd923400 {
		compatible = "qcom,mdss-edp";
		reg = <0xfd923400 0x700>,
			<0xfd8c2000 0x1000>;
		reg-names = "edp_base", "mmss_cc_base";
		vdda-supply = <&pm8941_l12>;
		gpio-panel-en = <&msmgpio 58 0>;
		qcom,panel-lpg-channel = <7>; /* LPG Channel 8 */
		qcom,panel-pwm-period = <53>;
		status = "disable";
	};