msm: vidc: enable low power mode based on firmware capability

firmware will send a threshold load as part of capabilities in
sys_init_done and driver will enable low power mode on encoder
if session load is more than threshold load to resolve video
session failures.

Change-Id: I6ddee773f0b40e3973c4583258941c4fdb70bd21
Signed-off-by: Deepak Kushwah <dkushwah@codeaurora.org>
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>