msm: camera: ope: Synchronize process cmd and flush request

There are chances that process cmd and flush request run in
parallel. This can cause bl request to get free and CDM to be
in reset state and finally lead to failure.

Avoid running process cmd and flush simultaneously.

CRs-Fixed: 2627548
Change-Id: I5fd28c2b517d91619c71f8f57ba91a621b585b22
Signed-off-by: Alok Chauhan <alokc@codeaurora.org>