CRAS: bt_io - Don't use software gain for BT input

software_volume_needed flag is also used for input to decide if
software gain can be used. When BT headset does audio recording,
HFP is used and that's low quality audio.
Applying positive gain on low quality audio could make the
experience worse, so don't do that.

BUG=chromium:799623
TEST=Execute 'cras_test_client --capture_file /tmp/1'
and then hit 'K'/'J'+'Enter' multiple times to change system
gain, verify that recorded volume doesn't chane.

Change-Id: I0922e7cad12abce520e57be386ce15f469f74d4e
Reviewed-on: https://chromium-review.googlesource.com/1140021
Commit-Ready: Hsinyu Chao <hychao@chromium.org>
Tested-by: Hsinyu Chao <hychao@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed