Device-Tree bindings for Atmel's HLCDC (High LCD Controller) MFD driver

Required properties:
 - compatible: value should be one of the following:
   "atmel,at91sam9n12-hlcdc"
   "atmel,at91sam9x5-hlcdc"
   "atmel,sama5d2-hlcdc"
   "atmel,sama5d3-hlcdc"
   "atmel,sama5d4-hlcdc"
   "microchip,sam9x60-hlcdc"
 - reg: base address and size of the HLCDC device registers.
 - clock-names: the name of the 3 clocks requested by the HLCDC device.
   Should contain "periph_clk", "sys_clk" and "slow_clk".
 - clocks: should contain the 3 clocks requested by the HLCDC device.
 - interrupts: should contain the description of the HLCDC interrupt line

The HLCDC IP exposes two subdevices:
 - a PWM chip: see ../pwm/atmel-hlcdc-pwm.txt
 - a Display Controller: see ../display/atmel/hlcdc-dc.txt

Example:

	hlcdc: hlcdc@f0030000 {
		compatible = "atmel,sama5d3-hlcdc";
		reg = <0xf0030000 0x2000>;
		clocks = <&lcdc_clk>, <&lcdck>, <&clk32k>;
		clock-names = "periph_clk","sys_clk", "slow_clk";
		interrupts = <36 IRQ_TYPE_LEVEL_HIGH 0>;

		hlcdc-display-controller {
			compatible = "atmel,hlcdc-display-controller";
			pinctrl-names = "default";
			pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb888>;
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				#address-cells = <1>;
				#size-cells = <0>;
				reg = <0>;

				hlcdc_panel_output: endpoint@0 {
					reg = <0>;
					remote-endpoint = <&panel_input>;
				};
			};
		};

		hlcdc_pwm: hlcdc-pwm {
			compatible = "atmel,hlcdc-pwm";
			pinctrl-names = "default";
			pinctrl-0 = <&pinctrl_lcd_pwm>;
			#pwm-cells = <3>;
		};
	};