audio: apply ramp on capture to remove plop.

Apply a volume to audio capture during the first milli seconds to
remove plop due to mic bias. A ramp is preferred to delaying capture
start or discarding frames to comply to CDD requirements for maximum
capture start time.

Change-Id: I4967e8568c8ded1967d98f88f5a526a9c576365f
1 file changed