CHROMIUM: ALSA: hda/ca0132 - configure DMIC gain block.

CHROMIUM: ALSA: hda/ca0132 - configure DMIC gain block.

Configure the DMIC input gain block when switching to use DMIC.  This
provides 20dB of additional input gain when using the built-in digital
microphone.

This should be changed to export a control to user-space, but keep it
simple for the R25 release.

BUG=chrome-os-partner:16865
TEST=arecord a reference signal and check that there is now 20dB of
gain applied.  Hangout and check that the participant on the other
side can hear you.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Change-Id: I2a748f5774e50e513b1107fc3119641aa227453b
Reviewed-on: https://gerrit.chromium.org/gerrit/41816
Reviewed-by: Chih-Chung Chang <chihchung@chromium.org>