ASoC: msm: Add support for voice over USB

Add routes to transfer voice packets to/from the
external modem to USB in APQ, and route the mixed
audio and voice streams to the extertal modem for
echo cancellation.

Change-Id: Ib5409ff1d8484fe0bdfb7205ad4f843b3dc818ac
Signed-off-by: Helen Zeng <xiaoyunz@codeaurora.org>