ASoC: qcom: Document LPASS CPU bindings

* Qualcomm Technologies LPASS CPU DAI

This node models the Qualcomm Technologies Low-Power Audio SubSystem (LPASS).

Required properties:

- compatible		: "qcom,lpass-cpu"

- clocks		: Must contain an entry for each entry in clock-names.

- clock-names		: A list which must include the following entries:

				* "ahbix-clk"

				* "mi2s-osr-clk"

				* "mi2s-bit-clk"

- interrupts		: Must contain an entry for each entry in

			  interrupt-names.

- interrupt-names	: A list which must include the following entries:

				* "lpass-irq-lpaif"

- pinctrl-N		: One property must exist for each entry in

			  pinctrl-names.  See ../pinctrl/pinctrl-bindings.txt

			  for details of the property values.

- pinctrl-names		: Must contain a "default" entry.

- reg			: Must contain an address for each entry in reg-names.

- reg-names		: A list which must include the following entries:

				* "lpass-lpaif"

Required subnodes:

- qcom,adsp		: Audio DSP sub-node

Optional Audio DSP subnode properties:

- status		: "disabled" indicates the adsp is not available.

Example:

lpass@28100000 {

	compatible = "qcom,lpass-cpu";

	clocks = <&lcc AHBIX_CLK>, <&lcc MI2S_OSR_CLK>, <&lcc MI2S_BIT_CLK>;

	clock-names = "ahbix-clk", "mi2s-osr-clk", "mi2s-bit-clk";

	interrupts = <0 85 1>;

	interrupt-names = "lpass-irq-lpaif";

	pinctrl-names = "default", "idle";

	pinctrl-0 = <&mi2s_default>;

	pinctrl-1 = <&mi2s_idle>;

	reg = <0x28100000 0x10000>;

	reg-names = "lpass-lpaif";

	qcom,adsp {

		status = "disabled";

	};

};