ALSA: ac97: add bus binding for codecs

Generic AC97 Device Properties

This documents describes the devicetree bindings for an ac97 controller child

node describing ac97 codecs.

Required properties:

-compatible : Must be "ac97,vendor_id1,vendor_id2

	      The ids shall be the 4 characters hexadecimal encoding, such as

	      given by "%04x" formatting of printf

-reg	    : Must be the ac97 codec number, between 0 and 3

Example:

ac97: sound@40500000 {

	compatible = "marvell,pxa270-ac97";

	reg = < 0x40500000 0x1000 >;

	interrupts = <14>;

	reset-gpios = <&gpio 95 GPIO_ACTIVE_HIGH>;

	#sound-dai-cells = <1>;

	pinctrl-names = "default";

	pinctrl-0 = < &pinctrl_ac97_default >;

	clocks = <&clks CLK_AC97>, <&clks CLK_AC97CONF>;

	clock-names = "AC97CLK", "AC97CONFCLK";

	#address-cells = <1>;

	#size-cells = <0>;

	audio-codec@0 {

		reg = <0>;

		compatible = "ac97,574d,4c13";

		clocks = <&fixed_wm9713_clock>;

		clock-names = "ac97_clk";

	}

};