USB: xhci: Don't touch xhci_td after it's freed.

On a successful transfer, urb->td is freed before the URB is ready to be
given back to the driver. Don't touch urb->td after it's freed. This bug
would have only shown up when xHCI debugging was turned on, and the freed
memory was quickly reused for something else.

Signed-off-by: Sarah Sharp <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/xhci-ring.c

···
 	if (urb) {
 		usb_hcd_unlink_urb_from_ep(xhci_to_hcd(xhci), urb);
 		xhci_dbg(xhci, "Giveback URB %p, len = %d, status = %d\n",
-				urb, td->urb->actual_length, status);
+				urb, urb->actual_length, status);
 		spin_unlock(&xhci->lock);
 		usb_hcd_giveback_urb(xhci_to_hcd(xhci), urb, status);
 		spin_lock(&xhci->lock);