ceph: update co-maintainers list in MAINTAINERS

Update the list of co-maintainers for Ceph file system following
Xiubo's departure.

Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Acked-by: Alex Markuze <amarkuze@redhat.com>
Acked-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Author: dubeyko

MAINTAINERS

@@ -5801,7 +5801,8 @@ F:	drivers/power/supply/cw2015_battery.c
 
 CEPH COMMON CODE (LIBCEPH)
 M:	Ilya Dryomov <idryomov@gmail.com>
-M:	Xiubo Li <xiubli@redhat.com>
+M:	Alex Markuze <amarkuze@redhat.com>
+M:	Viacheslav Dubeyko <slava@dubeyko.com>
 L:	ceph-devel@vger.kernel.org
 S:	Supported
 W:	http://ceph.com/
@@ -5812,8 +5813,9 @@ F:	include/linux/crush/
 F:	net/ceph/
 
 CEPH DISTRIBUTED FILE SYSTEM CLIENT (CEPH)
-M:	Xiubo Li <xiubli@redhat.com>
 M:	Ilya Dryomov <idryomov@gmail.com>
+M:	Alex Markuze <amarkuze@redhat.com>
+M:	Viacheslav Dubeyko <slava@dubeyko.com>
 L:	ceph-devel@vger.kernel.org
 S:	Supported
 W:	http://ceph.com/