drm/amd/display: disable S/G display on DCN 3.1.5

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

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2354
Cc: roman.li@amd.com
Cc: yifan1.zhang@amd.com
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -1503,7 +1503,6 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 		case IP_VERSION(3, 1, 2):
 		case IP_VERSION(3, 1, 3):
 		case IP_VERSION(3, 1, 4):
-		case IP_VERSION(3, 1, 5):
 		case IP_VERSION(3, 1, 6):
 			init_data.flags.gpu_vm_support = true;
 			break;