msm: vidc: Vote for zero ab value during Venus power collapse

Video driver should vote for zero ab value, when Venus firmware
is power collapsed. Without this change, if video is paused and
firmware goes in to power collapse, XO shutdown will not happen,
because video driver is still voting for non-zero ab values.

Change-Id: I483052531aef0e4b05973cdcdd3b0663fb711973
Signed-off-by: Arun Menon <avmenon@codeaurora.org>