AK4458 audio DAC

This device supports both I2C and SPI modes.

Required properties:

- compatible : "asahi-kasei,ak4458"
- reg : The I2C address of the device for I2C, the chip select number for SPI.
- asahi-kasei,pdn-gpios: A GPIO specifier for the GPIO controlling
	the power down & reset pin.
- asahi-kasei,mute-gpios: A GPIO specifier for the GPIO controlling
	the soft mute pin.

Example:

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