virtio serial port: fix to incomplete QOMify

Signed-off-by: NCao jin <caoj.fnst@cn.fujitsu.com>
Message-Id: <1452068575-21543-1-git-send-email-caoj.fnst@cn.fujitsu.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>

hw/char/virtio-serial-bus.c

@@ -798,7 +798,7 @@ static const TypeInfo virtser_bus_info = {
 
 static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
 {
-    VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);
+    VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(qdev);
 
     monitor_printf(mon, "%*sport %d, guest %s, host %s, throttle %s\n",
                    indent, "", port->id,