msm: vidc: fix DCVS logic issues

Initialize max_threshold to help DCVS to trigger
higher clock rate selection. Also fix an issue to
select lower clock rate when DCVS logic triggers it.
Update dcvs load appropriately to help other functions
which uses dcvs load.

Change-Id: If3a1c6813ea3e7eff4c8f19fc699511dc09eb491
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>