devmapper: add vbatts to MAINTAINERS

Signed-off-by: Vincent Batts <vbatts@redhat.com>

daemon/graphdriver/devmapper/MAINTAINERS

@@ -1 +1,2 @@
 Alexander Larsson <alexl@redhat.com> (@alexlarsson)
+Vincent Batts <alexl@redhat.com> (@vbatts)