msm: vidc: Fix video performance issues

This change fixes following performance issues.
    - Fix fps issue while calculating bus bandwidth.
    - Update buffer ownership calculation.
    - Update lower limit for DCVS clock reduction.

CRs-Fixed: 2117262
Change-Id: Ie58a325b5116c5bfc4620e8a04a481b43b7a8230
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>