usb: gadget: net2272: cleanup pci_register_driver() error path

In case pci_register_driver() fails it error will be 0 in case
platform_driver_register() was fine. Also without PCI
pci_register_driver() evaluates to 1 which is well, special. If
platform_driver_register() returns EINVAL or EBUSY we end up with 0.

Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>