SONY hw-mute control driver

Required properties:

- compatible : "sony,hw-mute"
- hw_mute-gpios : HW_MUTE output gpio
- fs_change_det-gpios : Fs change detect output gpio (optional)
- mute-off-delay : Delay time until hw_mute is enabled [ms] (optional)

Example:

/ {
	hw_mute {
		compatible = "sony,hw-mute";
		hw_mute-gpio = <&gpio4 0 GPIO_ACTIVE_HIGH>;
		fs_change_det-gpio = <&gpio4 22 GPIO_ACTIVE_HIGH>;
		mute-off-delay = <60>;
	};
};
