Original code was written to exit early on ehci_register()'s
success. As a part of e3eb0c729b, however, it was modified to to early
exit on failure instead. This resulted in VBUS being erroneously
disabled after EHCI controller was added, thus breaking USB on some
i.MX boards (confirmed on ZII's RDU2).

Fixes: e3eb0c729b ("usb: host: ehci: add ehci_unregister()")
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>