Freescale i.MX audio complex PDM microphone

Required properties:
- compatible: "fsl,imx-pdm-mic"
- model: The user-visible name of this sound complex
- audio-cpu : The phandle of the i.MX SAI controller
- decimation : The PDM decimation factor <64>

Example:

sound-pdm {
	compatible = "fsl,imx-pdm-mic";
	model = "imx-pdm-audio";
	audio-cpu = <&sai3>;
	decimation = <64>;
};