msm: camera: ope: Avoid dead lock during flush

During flush OPE driver takes lock on OPE context and
calls the CDM flush, in which CDM notifies OPE for all
pending requests. If at the same time CDM is notifying
OPE for successful request that thread also tries to
take lock on OPE context. CDM also tries to takes lock
on CDM client in each notify call. Due to which,
dead lock is occurring.

So taking the lock on OPE context in OPE flush after
CDM flush.

CRs-Fixed: 2520602
Change-Id: I6ae9105d33a49a638141973cdd6a4a99621dc4c5
Signed-off-by: Rishabh Jain <risjai@codeaurora.org>