MAINTAINERS: add Xiubo Li as cephfs co-maintainer

Xiubo has been doing stellar kernel work lately, and has graciously
volunteered to help with maintainer duties. Add him on as co-maintainer
in for ceph.ko and libceph.ko.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

MAINTAINERS

@@ -4446,6 +4446,7 @@ F:	drivers/power/supply/cw2015_battery.c
 CEPH COMMON CODE (LIBCEPH)
 M:	Ilya Dryomov <idryomov@gmail.com>
 M:	Jeff Layton <jlayton@kernel.org>
+M:	Xiubo Li <xiubli@redhat.com>
 L:	ceph-devel@vger.kernel.org
 S:	Supported
 W:	http://ceph.com/
@@ -4456,6 +4457,7 @@ F:	net/ceph/
 
 CEPH DISTRIBUTED FILE SYSTEM CLIENT (CEPH)
 M:	Jeff Layton <jlayton@kernel.org>
+M:	Xiubo Li <xiubli@redhat.com>
 M:	Ilya Dryomov <idryomov@gmail.com>
 L:	ceph-devel@vger.kernel.org
 S:	Supported