MAINTAINERS: Add myself as a migration submaintainer

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20170124100437.18200-1-dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

MAINTAINERS

@@ -1420,6 +1420,7 @@ F: scripts/checkpatch.pl
 Migration
 M: Juan Quintela <quintela@redhat.com>
 M: Amit Shah <amit.shah@redhat.com>
+M: Dr. David Alan Gilbert <dgilbert@redhat.com>
 S: Maintained
 F: include/migration/
 F: migration/