WM8731 audio CODEC

This device supports both I2C and SPI (configured with pin strapping
on the board).

Required properties:

  - compatible : "wlf,wm8731"

  - reg : the I2C address of the device for I2C, the chip select
          number for SPI.

Example:

wm8731: codec@1a {
	compatible = "wlf,wm8731";
	reg = <0x1a>;
};

Available audio endpoints for an audio-routing table:
 * LOUT: Left Channel Line Output
 * ROUT: Right Channel Line Output
 * LHPOUT: Left Channel Headphone Output
 * RHPOUT: Right Channel Headphone Output
 * LLINEIN: Left Channel Line Input
 * RLINEIN: Right Channel Line Input
 * MICIN: Microphone Input