Apple machines with multiple speakers typically have the shutdown pin of
the digital amplifier codecs wired up to a single GPIO. This is apparently
problematic for Linux and Asahi Linux changed thei

Apple machines with multiple speakers typically have the shutdown pin of
the digital amplifier codecs wired up to a single GPIO. This is apparently
problematic for Linux and Asahi Linux changed their device trees to use a
regulator instead to such that reference counting makes sure that shutdown
isn't asserted until all codecs are ready for it. Follow suit, even though
our regulator code doesn't do the proper reference counting yet.

ok patrick@

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Add mute control. This makes the mute button on laptops that use
tascodec(4) work.

ok tobhe@

Set default volume to -30 dB instead of using the hardware default of 0 dB
(which means maximum volume).

ok patrick@, ratchov@

Add a callback for setting the TDM slot used by an audio codec.
Implement this callback in tascodec(4) such that we can pick the audio
channel that it outputs. This will override the default which i

Add a callback for setting the TDM slot used by an audio codec.
Implement this callback in tascodec(4) such that we can pick the audio
channel that it outputs. This will override the default which is to
downmix stereo input from TDM channels 0 and 1 to mono output.

ok ratchov@

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The GPIO pin on Apple M1 systems is actually connected to the SDZ pin, which
is reflected in more recent device trees. Adjust the driver accordingly.

ok patrick@

Constify struct {audio,midi,radio,video}_hw_if. No functional change.

ok mpi@ ratchov@ "More const is good" deraadt@

Use iic_is_compatible(9) and use the more generic compatible string to
match the device.

ok visa@

Add tascodec(4), a driver for the TI TAS2770/TAS5770 digital audio
amplifier codec found on Apple M1 Macs.

ok patrick@, ratchov@