msm: vidc: Handle bitdepth event change

Venus firmware will raise an insufficient event
and bitdepth information whenever it detects a
bitdepth change. Video driver will inturn raise an
event and inform the new bitdepth to v4l2 client.

Change-Id: Ia089dededb81b782e38c59ed9bb8063b04657af1
Signed-off-by: Arun Menon <avmenon@codeaurora.org>