Revert "drm/amd/display: disable S/G display on DCN 3.1.4"

This reverts commit 9aa15370.

This is fixed now so we can re-enable S/G display on DCN
3.1.4.

Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>