drm/qxl: Do not leak memory if qxl_release_list_add fails

If the function fails reference counter to the object is not decremented
causing leaks.
This is hard to spot as it happens only on very low memory situations.
Signed-off-by: NFrediano Ziglio <fziglio@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/qxl/qxl_ioctl.c

@@ -122,8 +122,10 @@ static struct qxl_bo *qxlhw_handle_to_bo(struct qxl_device *qdev,
 	qobj = gem_to_qxl_bo(gobj);
 
 	ret = qxl_release_list_add(release, qobj);
-	if (ret)
+	if (ret) {
+		drm_gem_object_unreference_unlocked(gobj);
 		return NULL;
+	}
 
 	return qobj;
 }