audio: acquire lock for compress voip close input/output stream

compress voip close input/output function is making call
to same api "voip_call_stop()" which will close both Rx
and Tx path. Now mmap->status for both pcm devices will
be NULL. Meantime  if any call to pcm_get_htimestamp()"
will lead to crash

Change-Id: Icd6953265d791b26b180744721ddb61bd33933aa
CRs-fixed: 988730
1 file changed