[NET]: Fix sparse warnings

Of this type, mostly:

CHECK   net/ipv6/netfilter.c
net/ipv6/netfilter.c:96:12: warning: symbol 'ipv6_netfilter_init' was not declared. Should it be static?
net/ipv6/netfilter.c:101:6: warning: symbol 'ipv6_netfilter_fini' was not declared. Should it be static?

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ebb8654..1afb080 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4229,7 +4229,7 @@
 				 */
 				if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
 				    !tp->srtt)
-					tcp_ack_saw_tstamp(sk, 0, 0);
+					tcp_ack_saw_tstamp(sk, NULL, 0);
 
 				if (tp->rx_opt.tstamp_ok)
 					tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;