ASoC: msm: Add incall music delivery support

Add one backend DAI, and add one mixer control to route playback stream
to the new backend DAI. Start/stop playback commands will be sent to CVD
if starting/stopping playback, after voice call is established.

Change-Id: I334f1894ac0800e6a71fa7e20ac634b1b05cc414
Signed-off-by: Helen Zeng <xiaoyunz@codeaurora.org>
11 files changed