usb: Move determination of TT hub address/port into separate function

Start split and complete split tokens need the hub address and the
downstream port of the first HS hub (device view).

The core of the function was duplicated in both host/ehci_hcd and
musb-new/usb-compat.h.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>