usb: usb251xb: Drop some unused defines

The five removed symbols are unused since they were introduced in commit
3ec72a2a ("usb: misc: add USB251xB/xBi Hi-Speed Hub Controller
Driver") back in 2017.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20191023105250.16537-1-u.kleine-koenig@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>