Freescale i.MX audio complex with SGTL5000 codec

Required properties:
- compatible : "fsl,imx-audio-sgtl5000"
- model : The user-visible name of this sound complex
- ssi-controller : The phandle of the i.MX SSI controller
- audio-codec : The phandle of the SGTL5000 audio codec
- 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, SGTL5000 pins, and the jacks on the board:

  Power supplies:
   * Mic Bias

  SGTL5000 pins:
   * MIC_IN
   * LINE_IN
   * HP_OUT
   * LINE_OUT

  Board connectors:
   * Mic Jack
   * Line In Jack
   * Headphone Jack
   * Line Out Jack
   * Ext Spk

- mux-int-port : The internal port of the i.MX audio muxer (AUDMUX)
- mux-ext-port : The external port of the i.MX audio muxer

Note: The AUDMUX port numbering should start at 1, which is consistent with
hardware manual.

Example:

sound {
	compatible = "fsl,imx51-babbage-sgtl5000",
		     "fsl,imx-audio-sgtl5000";
	model = "imx51-babbage-sgtl5000";
	ssi-controller = <&ssi1>;
	audio-codec = <&sgtl5000>;
	audio-routing =
		"MIC_IN", "Mic Jack",
		"Mic Jack", "Mic Bias",
		"Headphone Jack", "HP_OUT";
	mux-int-port = <1>;
	mux-ext-port = <3>;
};