* Analog Devices AD7949/AD7682/AD7689

Required properties:
 - compatible: Should be one of
	* "adi,ad7949"
	* "adi,ad7682"
	* "adi,ad7689"
 - reg: spi chip select number for the device
 - vref-supply: The regulator supply for ADC reference voltage

Example:
adc@0 {
	compatible = "adi,ad7949";
	reg = <0>;
	vref-supply = <&vdd_supply>;
};