ppdev: ppdev_init: do not return zero in case of failure

Error handling of parport_register_driver() in ppdev_init()
is broken because it deallocates all resources but still
returns zero.

Currently parport_register_driver() always succeeds.
Nevertheless it is worth to fix the issue.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>