asoc: lsm: free confidence_levels memory to avoid memory leakage

prtd->lsm_client->confidence_levels is allocated in
msm_lsm_get_conf_levels and not freed in msm_lsm_set_conf.
Make this change to free this memory.

Change-Id: I617703b36c13e065fdf995e89121c442b32b08f3
Signed-off-by: Meng Wang <mengw@codeaurora.org>