usb: zap pdev from usbport

It isn't needed any more.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/hw/usb-bus.c b/hw/usb-bus.c
index f89176b..6e2e5fd 100644
--- a/hw/usb-bus.c
+++ b/hw/usb-bus.c
@@ -120,11 +120,10 @@
 }
 
 void usb_register_port(USBBus *bus, USBPort *port, void *opaque, int index,
-                       USBDevice *pdev, USBPortOps *ops, int speedmask)
+                       USBPortOps *ops, int speedmask)
 {
     port->opaque = opaque;
     port->index = index;
-    port->pdev = pdev;
     port->opaque = opaque;
     port->index = index;
     port->ops = ops;