msm: camera: Adds state variable in mem manager

Add state variable for camera mem manager to show initialization status.
Ensure that all operations are rejected before initialization.

Change-Id: I1ddbaaf6fbed59e4804476562c97f6895d99e916
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>
Signed-off-by: Raja Mallik <rmallik@codeaurora.org>