drm/radeon: check return value of radeon_fence_emit

Function radeon_fence_emit() returns -ENOMEM if there is no enough
memory. And in this case, function radeon_ring_unlock_undo() rather than
function radeon_ring_unlock_commit() should be called. However, in
function radeon_test_create_and_emit_fence(), the return value of
radeon_fence_emit() is ignored. This patch adds the check.

Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Pan Bian <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_test.c

···
 			DRM_ERROR("Failed to lock ring A %d\n", ring->idx);
 			return r;
 		}
-		radeon_fence_emit(rdev, fence, ring->idx);
+		r = radeon_fence_emit(rdev, fence, ring->idx);
+		if (r) {
+			DRM_ERROR("Failed to emit fence\n");
+			radeon_ring_unlock_undo(rdev, ring);
+			return r;
+		}
 		radeon_ring_unlock_commit(rdev, ring, false);
 	}
 	return 0;