drm/amd/display: Add missed wait_for_prev_commits.

Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -3111,6 +3111,7 @@ int amdgpu_dm_atomic_check(struct drm_device *dev,
 							surface);
 
 				need_to_validate = true;
+				wait_for_prev_commits = true;
 			}
 		}
 	}