ASoC: pxa: add binding for pxa2xx-ac97 audio complex

Marvell PXA2xx audio complex

This descriptions matches the AC97 controller found in pxa2xx and pxa3xx series.

Required properties:

  - compatible: should be one of the following:

    "marvell,pxa250-ac97"

    "marvell,pxa270-ac97"

    "marvell,pxa300-ac97"

  - reg: device MMIO address space

  - interrupts: single interrupt generated by AC97 IP

  - clocks: input clock of the AC97 IP, refer to clock-bindings.txt

Optional properties:

  - pinctrl-names, pinctrl-0: refer to pinctrl-bindings.txt

  - reset-gpios: gpio used for AC97 reset, refer to gpio.txt

Example:

	ac97: sound@40500000 {

		compatible = "marvell,pxa250-ac97";

		reg = < 0x40500000 0x1000 >;

		interrupts = <14>;

		reset-gpios = <&gpio 113 GPIO_ACTIVE_HIGH>;

		#sound-dai-cells = <1>;

		pinctrl-names = "default";

		pinctrl-0 = < &pmux_ac97_default >;

	};