usb-hub: wakeup on detach too.

When detaching devices from the usb hub we must wakeup too,
otherwise the host misses the detach event.

Commit 4a33a9ea06f6fbb08d8311a7cfed72975344f9ab does the
same for device attach.

Found by hkran@linux.vnet.ibm.com

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb-hub.c

@@ -171,6 +171,8 @@ static void usb_hub_detach(USBPort *port1)
     USBHubState *s = port1->opaque;
     USBHubPort *port = &s->ports[port1->index];
 
+    usb_wakeup(&s->dev);
+
     /* Let upstream know the device on this port is gone */
     s->dev.port->ops->child_detach(s->dev.port, port1->dev);