msm: camera: Add per instance lock in to serialize

Add per instance lock to serialize stream operation.
Protect unpredicted crash on video recording by serializing ops.
Instead of only using the vid_lock to protect the video node,
we need inst lock to serialize the stream operation, too.
This commit increases the stability during recording.

Change-Id: I4f6dcb6637eb700df04f30a102aada4fdec9f2d1
CRs-Fixed: 363221
Signed-off-by: Peter Liu <pingchie@codeaurora.org>