usb: usb251xb: Add support for USB2422

The USB2422 uses a different package that the USB251x and only comes in
a variant with 2 downstream ports. Other than that it is software
compatible.

Tested-by: Carsten Stelling <carsten.stelling@goerlitz.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20191023105250.16537-3-u.kleine-koenig@pengutronix.de


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