msm: vidc: Tune video DCVS for msm8996

Make changes to buffer count logic as part of tuning video DCVS for
msm8996.  As part of these changes, also consider buffers still
referenced to by firmware as being owned by firmware.

Change-Id: If4e81faf4fa2f34405fa9fd4f0c1e863f4d158b4
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>