[NETNS][IPV4] tcp - make proc handle the network namespaces

This patch, like udp proc, makes the proc functions to take care of
which namespace the socket belongs.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -1328,6 +1328,7 @@ struct tcp_seq_afinfo {
 };
 
 struct tcp_iter_state {
+	struct net              *net;
 	sa_family_t		family;
 	enum tcp_seq_states	state;
 	struct sock		*syn_wait_sk;