drm/msm/sde: don't setup AVR for displays not supporting qsync

Avoid calling avr setup function for panels which don't support this
feature.  Only video mode DSI panels with a valid setting for the
qcom,mdss-dsi-qsync-min-refresh-rate node in the device tree should
call in to this function.

Change-Id: Ia624576ca74bc93de6cf238cb7b577c5e8897bc1
Signed-off-by: Steve Cohen <cohens@codeaurora.org>