drm/amdgpu/display: re-enable freesync video patches

Since this is a "revert of a revert", the end effect is that freesync
video is back to its original state, the way it was before the first
revert.

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>