MAINTAINERS: Add xen-usb.c to Xen section

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Paul Durrant <paul@xen.org>
Message-Id: <20200406165043.1447837-1-anthony.perard@citrix.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 9d156d7..839959f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -440,6 +440,7 @@
 F: hw/char/xen_console.c
 F: hw/display/xenfb.c
 F: hw/net/xen_nic.c
+F: hw/usb/xen-usb.c
 F: hw/block/xen*
 F: hw/block/dataplane/xen*
 F: hw/xen/