MAINTAINERS: add missing entry for vhost

Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

MAINTAINERS

@@ -1034,6 +1034,7 @@ vhost
 M: Michael S. Tsirkin <mst@redhat.com>
 S: Supported
 F: hw/*/*vhost*
+F: docs/interop/vhost-user.txt
 
 virtio
 M: Michael S. Tsirkin <mst@redhat.com>