msm: camera: Fix Use after free bug in msm_vb2.c

There is no syncronization between msm_vb2_get_buf
and msm_delete_stream which can lead to use after
free.
Fixed it by using read/write lock.

Change-Id: Icff5cd81b1a4e9c28f19936dec570751feab0ccf
Signed-off-by: Manish Poddar <mpoddar@codeaurora.org>
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>
Signed-off-by: Andy Sun <bins@codeaurora.org>