msm: vidc: Release device lock while returning error from pm handler

Without this change, we will see a deadlock in the Venus hfi.
If the venus power handler thread gets kicked in after the
core has gone in to bad state, then power collapse will be
skipped. But the hfi device->lock was not released before
the return. Subsequently if the video driver receives a
suspend command, it will first try to acquire the device->lock,
and will be stuck there forever. This causes the entity which
invoked suspend operation on the video driver to timeout
and crash the device.

Change-Id: Ia6a0082724dffc6166f6fed0a79eb6526e44684b
Signed-off-by: Arun Menon <avmenon@codeaurora.org>