[NETFILTER]: Extend nf_inet_addr with in{,6}_addr

Extend union nf_inet_addr with struct in_addr and in6_addr. Useful
because a lot of in-kernel IPv4 and IPv6 functions use
in_addr/in6_addr.

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>