list MST as pci layer maintainer

List MST as PCI maintainer so that people know
whom to Cc on patches.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

MAINTAINERS

@@ -75,7 +75,7 @@ Main loop                 Fabrice Bellard (new maintainer needed)
 TCG                       Fabrice Bellard
 IDE device                ?
 SCSI device               Paul Brook
-PCI layer                 ?
+PCI layer                 Michael S. Tsirkin
 USB layer                 ?
 Block layer               ?
 Graphic layer             ?