msm: vidc: Enable venus power management

Besides clock gating, turn venus core power off
if the core stays idle for given amount of time.
Powering off venus core involves telling TZ to
suspend venus core, detach IOMMU, disable GDSC
regulator, unvote DDR/OCMEM buses.

Turn it on again when driver starts processing new
commands before enabling clocks.

Protect clock and power states and operations
with a common lock.

Change-Id: I49654069920ddaae0e2f8792b14cd1bfeb431c34
Signed-off-by: Sachin Shah <sachins@codeaurora.org>