ASoC: msm: qdsp6v2: Handle call end properly

The commands for detaching CVS session and unmapping
data exchange memory are sent to LPASS when a voip call ends.
When tearing down a call, the command for unmapping calibration
memory will be sent to LPASS if there is one call existed.

Change-Id: I49abe68aee71931884ee620593297d6b98ba59ed
CRs-fixed: 487075
Signed-off-by: Helen Zeng <xiaoyunz@codeaurora.org>