msm: camera: fd: Check open_count before CDM streamoff

Check for unbalanced open before calling CDM streamoff to
avoid unbalanced CDM streamoff. The imbalance existed because
in init(), open_count was not getting incremented once positive.

Change-Id: I962536819b74fe7d1e8247608bd69e3c7d34caab
Signed-off-by: Harsh Shah <harshs@codeaurora.org>