audio: added support for dual mic capture

Added support for simultaneous capture of front and back mic.

Added device definitions for dual mic config for voice recognition use
case: no pre processing enabled.

stream->channels() reports actual channel mask instead of recontructing
it from channel count.

TODO: check if ACDB settings copied from single mic voice recognition
are correct.

Change-Id: I41282d0af5deb256ef68ec17ee34f5aae7807a6f
6 files changed
tree: 66a7f338c566c6ff6534ae0438408d59d347813d
  1. alsa_sound/
  2. libalsa-intf/
  3. Android.mk