v4l2transform: Fix potential deadlock due to missing break

CID 1212131
diff --git a/sys/v4l2/gstv4l2transform.c b/sys/v4l2/gstv4l2transform.c
index 6928a39..5e3ec56 100644
--- a/sys/v4l2/gstv4l2transform.c
+++ b/sys/v4l2/gstv4l2transform.c
@@ -536,6 +536,7 @@
       GST_DEBUG_OBJECT (self, "flush start");
       gst_v4l2_object_unlock (self->v4l2output);
       gst_v4l2_object_unlock (self->v4l2capture);
+      break;
     case GST_EVENT_FLUSH_STOP:
       GST_DEBUG_OBJECT (self, "flush stop");
       gst_v4l2_object_unlock_stop (self->v4l2output);