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

Causes flickering or white screens in some configurations.
Disable it for now until we can fix the issue.

Cc: roman.li@amd.com
Cc: yifan1.zhang@amd.com
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>