ieee1394: eth1394: revert parent device to that in 2.6.20

After ieee1394 was converted away from class_device like the networking
subsystem was already in 2.6.21, eth1394's device may point to the
fw-host device as its parent again like in 2.6.20.

This affects userspace tools which examine the sysfs representation of
eth1394's device.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>