[IPV4/IPV6]: Fix inet{,6} device initialization order.

It is important that we only assign dev->ip{,6}_ptr
only after all portions of the inet{,6} are setup.

Otherwise we can receive packets before the multicast
spinlocks et al. are initialized.

Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>