MAINTAINERS: add Alex Aring as Reviewer for file locking code

Alex helps co-maintain the DLM code and did some recent work to fix up
how lockd and GFS2 work together. Add him as a Reviewer for file locking
changes.
Acked-by: Alexander Aring <aahringo@redhat.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

MAINTAINERS

@@ -8165,6 +8165,7 @@ F:	include/uapi/scsi/fc/
 FILE LOCKING (flock() and fcntl()/lockf())
 M:	Jeff Layton <jlayton@kernel.org>
 M:	Chuck Lever <chuck.lever@oracle.com>
+R:	Alexander Aring <alex.aring@gmail.com>
 L:	linux-fsdevel@vger.kernel.org
 S:	Maintained
 F:	fs/fcntl.c