asoc: msm-pcm: Added lock in controls _put() and _get() callback

There is race condition around private data used in put() and get()
of few mixer ctls with close() callback. Added global mutex lock and
code changes to protect such critical section by accessing such lock.

Change-Id: Ic160b0c7c29d0ea5d517b3bacc53828d8d61e085
Signed-off-by: Ajit Pandey <ajitp@codeaurora.org>