Add a control "Mic Playback Volume" that allows the user to control the
MIC gain stage (common for Mic1 and Mic2) leading to the output mixer.
Signed-off-by: NDanny Milosavljevic <dannym@scratchpost.org>
Reviewed-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMark Brown <broonie@kernel.org>