ASoC: lsm-client: Fix null pointer access when no LSM session

When no LSM session is active, return from msm_lsm_close
and avoid null pointer dereference.

Change-Id: I9f57c08e080497765eaefef0c031bbf956c02914
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>