added comments for A2020, increase mic volume, decrease earspeaker volume to prevent acoustic echo

Change-Id: I6e141fb6c15ad3ccab01a7c84c95a895d6542c50
Reduce Acoustic echo

Change-Id: I6f60584ed523252b2ac0034078642a559b17ff3a
Merge pull request #10 from jied83/jellybean

added comments for A2020, increase mic volume, decrease earspeaker volum...