ASoC: samsung: Document Odroid X2/U3 audio subsystem bindings

Samsung Exynos Odroid X2/U3 audio complex with MAX98090 codec

Required properties:

 - compatible : "samsung,odroidx2-audio" - for Odroid X2 board,

		"samsung,odroidu3-audio" - for Odroid U3 board

 - samsung,model : the user-visible name of this sound complex

 - samsung,i2s-controller : the phandle of the I2S controller

 - samsung,audio-codec : the phandle of the MAX98090 audio codec

 - samsung,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 for sources and sinks are the MAX98090's pins (as

   documented in its binding), and the jacks on the board

   For Odroid X2:

     * Headphone Jack

     * Mic Jack

     * DMIC

   For Odroid U3:

     * Headphone Jack

     * Speakers

Example:

sound {

	compatible = "samsung,odroidu3-audio";

	samsung,i2s-controller = <&i2s0>;

	samsung,audio-codec = <&max98090>;

	samsung,model = "Odroid-X2";

	samsung,audio-routing =

		"Headphone Jack", "HPL",

		"Headphone Jack", "HPR",

		"IN1", "Mic Jack",

		"Mic Jack", "MICBIAS";

};