msm: camera: Use mutex lock to avoid race condition

Use mutex lock before using queuing ioctls like
queuing, dequeing buffers to avoid race condition.

Change-Id: I59c70f2abe3daddf38761a2f17671d3d49f43989
CRs-fixed: 2038086
Signed-off-by: Terence Ho <terenceh@codeaurora.org>