According to a forum user, there's an audible click when changing
the volume between -32 and -32.5 dB with some headphones. Fix this
by not (ab)using the DAC digital mixer for volume control.
The mixer only provides an extra -6 dB of hardware volume range,
so the only side effect is that software volume will now kick in
at -32 dB instead of -38 dB.
Change-Id: If24d9bc0058eff3c1a29aefb155a2e378522623c
Some audiohw API calls are shared between playback and recording,
eg. frequency settings. Implementing these in the DAC driver won't
work for the M3K, as it uses a separate codec for microphone input.
Change-Id: Ieb0a267f8a81b9e2bbf0bbca951c5778f8dcd203
