drm:msm:sde: update avr mode config during commit prepare

Add changes to support avr mode config update during
prepare commit which happens before gpu fence wait
for input buffers.

Change-Id: Ib2cb5b7e1f10501914c003f6cf066b85048f79d4
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>