ASoC: adau17x1: Add adau17x1 bindings document

Analog Devices ADAU1361/ADAU1461/ADAU1761/ADAU1961/ADAU1381/ADAU1781

Required properties:

 - compatible:		Should contain one of the following:

			"adi,adau1361"

			"adi,adau1461"

			"adi,adau1761"

			"adi,adau1961"

			"adi,adau1381"

			"adi,adau1781"

 - reg:			The i2c address. Value depends on the state of ADDR0

			and ADDR1, as wired in hardware.

Examples:

#include <dt-bindings/sound/adau17x1.h>

	i2c_bus {

		adau1361@38 {

			compatible = "adi,adau1761";

			reg = <0x38>;

		};

	};