msm: camera: add different mutex lock for camera close

when camera_v4l2_close is called for one of the stream
and say backend is taking more time to delete the stream
and in between mediaserver crashes which call close camera
which lead to race condition. To avoid this added a lock
for close camera.

Change-Id: Idc4a72fd1d639619fafd3e2856d5bb502785c0bf
Signed-off-by: Manish Poddar <mpoddar@codeaurora.org>