msm: camera: Handle race condition on stream buffer ops

During camera tear down seq HAL stops the stream and unreg buffers.
In this scenario, if back end modules doesn't stream off and still
access the stream buffers there occurs race condition when tearing
down the stream vs accessing stream buffers. Lock the stream while
tearing down.

Change-Id: Ie0f64efc790a0ca0c0399863417c730af91ac36b
Signed-off-by: Azam Sadiq Pasha Kapatrala Syed <akapatra@codeaurora.org>