drm/amd/display: Re-enable SubVP high refresh

Re-enable SubVP high refresh now that it is fixed
for displays with high refresh rates.

Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Saaem Rizvi <SyedSaaem.Rizvi@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>