ASoC: msm: qdsp6v2: Fix mute/unmute issues in DSDA

Mute/unmute is not getting reflected in call that was
switched to ACTIVE from CALL_HOLD. lch_mode variable
is not reset after LCH_STOP is received is causing the
issue. Fix this issue by resetting the lch_mode when
LCH_STOP is received.

CRs-Fixed: 652400
Change-Id: Ide4a6a399accd84384199e723cdeabb722ab41e1
Signed-off-by: Venkata Narendra Kumar Gutta <vgutta@codeaurora.org>