msm: vidc: Handle failure cases in venus power down sequence

Disabling clock in tzbsp suspend failed case is resulting
in write register failures afterwards. There is no need of
clocks enable and disable temporarily in power down sequence
because clocks will never be disabled during video use cases.
Similarly handle other error cases in power down sequence.
Cancel the pending delayed work in work_queue before the last
video usecase is closed to avoid scheduling of work unnecessarily.

Change-Id: I226b76f97ed8a6ec1db83a9c1a9cf604b5a953bb
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>