msm: vidc: Use luma bitdepth for pixel depth handling

Firmware will report both luma and chroma bitdepth
info to driver as part of bitdepth sequence change
event. Driver needs to use only luma bitdepth info
to determine output bitdepth type. Also incorporate
the changed hfi value for HFI_BITDEPTH_10 because of
addition of HFI_BITDEPTH_9.

Change-Id: I5c54a3a2c1fd043422132c60bb373e8ad6cb1623
Signed-off-by: Arun Menon <avmenon@codeaurora.org>