AK4458 audio DAC

This device supports I2C mode.

Required properties:

- compatible : "asahi-kasei,ak4458" or "asahi-kasei,ak4497"
- reg : The I2C address of the device for I2C

Optional properties:
- reset-gpios: A GPIO specifier for the power down & reset pin
- mute-gpios: A GPIO specifier for the soft mute pin

Example:

&i2c {
	ak4458: dac@10 {
		compatible = "asahi-kasei,ak4458";
		reg = <0x10>;
		reset-gpios = <&gpio1 10 GPIO_ACTIVE_LOW>
		mute-gpios = <&gpio1 11 GPIO_ACTIVE_HIGH>
	};
};