ctc: make use of alloc_netdev()

Currently ctc-device initialization is broken (kernel bug in
ctc_new_device).
The new network namespace code reveals a deficiency of the
ctc driver. It should make use of alloc_netdev() as described
in Documentation/networking/netdevices.txt.

Signed-off-by: Peter Tiedemann <ptiedem@de.ibm.com>
Signed-off-by: Ursula Braun <braunu@de.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>