Fix device validation
Fix device validation

First, we must not free the parent pointer. See libudev docs. We do not own a
reference to unless we call udev_device_ref().

Second: sysnum may not always be available so retrieve it from sysname.

Signed-off-by: David Herrmann <fb53b2ddb8d141e0cb39d7c67c2f81b6bc2eb0f7@googlemail.com>

dnschneid/xf86-input-xwiimote,dvdhrm/xf86-input-xwiimote,dnschneid/xf86-input-xwiimote,dvdhrm/xf86-input-xwiimote