usb: ehci: Properly set hub devnum and portnr with usb-1 hubs in the chain

For full / low speed devices we need to get the devnum and portnr of the tt,
so of the first upstream usb-2 hub, not of the parent device (which may be a
usb-1 hub).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>