ASoC: atmel-classd: DT binding for Class D audio amplifier driver

* Atmel ClassD driver under ALSA SoC architecture

Required properties:

- compatible

	Should be "atmel,sama5d2-classd".

- reg

	Should contain ClassD registers location and length.

- interrupts

	Should contain the IRQ line for the ClassD.

- dmas

	One DMA specifiers as described in atmel-dma.txt and dma.txt files.

- dma-names

	Must be "tx".

- clock-names

	Tuple listing input clock names.

	Required elements: "pclk", "gclk" and "aclk".

- clocks

	Please refer to clock-bindings.txt.

Optional properties:

- pinctrl-names, pinctrl-0

	Please refer to pinctrl-bindings.txt.

- atmel,model

	The user-visible name of this sound complex.

	The default value is "CLASSD".

- atmel,pwm-type

	PWM modulation type, "single" or "diff".

	The default value is "single".

- atmel,non-overlap-time

	Set non-overlapping time, the unit is nanosecond(ns).

	There are four values,

	<5>, <10>, <15>, <20>, the default value is <10>.

	Non-overlapping will be disabled if not specified.

Example:

classd: classd@fc048000 {

		compatible = "atmel,sama5d2-classd";

		reg = <0xfc048000 0x100>;

		interrupts = <59 IRQ_TYPE_LEVEL_HIGH 7>;

		dmas = <&dma0

			(AT91_XDMAC_DT_MEM_IF(0) | AT91_XDMAC_DT_PER_IF(1)

			| AT91_XDMAC_DT_PERID(47))>;

		dma-names = "tx";

		clocks = <&classd_clk>, <&classd_gclk>, <&audio_pll_pmc>;

		clock-names = "pclk", "gclk", "aclk";

		pinctrl-names = "default";

		pinctrl-0 = <&pinctrl_classd_default>;

		atmel,model = "classd @ SAMA5D2-Xplained";

		atmel,pwm-type = "diff";

		atmel,non-overlap-time = <10>;

};