Freescale i.MX audio complex with AK4458 DAC

Required properties:

- compatible	: "fsl,imx-audio-ak4458"
- model		: The user-visible name of this sound complex
- audio-cpu	: The phandle of CPU DAI
- audio-codec	: The phandle of the AK4458 audio DAC
- audio-routing : A list of the connections between audio components. Each entry
  is a pair of strings, the first being the connection's sink, the second being
  the connection's source. Valid names could be power supplies, AK4458 pins,
  and the jacks on the board.

Example:

sound {
       compatible = "fsl,imx-audio-ak4458";
       model = "ak4458-audio";
       audio-cpu = <&sai1>;
       audio-codec = <&codec>;
       audio-routing =
               "AOUTL1", "Playback",
               "AOUTR1", "Playback",
               "AOUTL2", "Playback",
               "AOUTR2", "Playback",
               "AOUTL3", "Playback",
               "AOUTR3", "Playback",
               "AOUTL4", "Playback",
               "AOUTR4", "Playback";
};