Revert "drm/amd: Remove freesync video mode amdgpu parameter"

This reverts commit e94e787e.

This conflicts with how compositors want to handle VRR.  Now
that compositors actually handle VRR, we probably don't need
freesync video.

Closes: drm/amd#2985


Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>