Linux requests the reset gpio optional by using devm_gpiod_get_optional().
We need to do this here too because the reset can be a global shared
reset line e.g. board por. We haven't such a helper so just drop the
final else path.

Fixes: 937fa50d9c ("usb: Port Microchip USB251x USB hub driver from Linux")
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>