msm: camera: Allow driver file to be opend only once.

Use proper synchronization to ensure driver file is opened
only once.

CRs-Fixed: 2023513
Bug: 62378684
Change-Id: I71e55e2d487fe561d3f596590b3e8102c5e921b5
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>