msm: vidc: Disable bitrate scaling if DCVS is enabled

Bitrate scaling will try to bump up Venus clock frequency
if there is a bitrate spike, whereas DCVS tries to bring down
the Venus clock frequency to save power. Hence, disable
bitrate scaling when DCVS is enabled.

Change-Id: I91361382803eb7e46c1db44b9cd5960d07e45a3d
Signed-off-by: Arun Menon <avmenon@codeaurora.org>