net: Kill hold_net release_net

hold_net and release_net were an idea that turned out to be useless.
The code has been disabled since 2008.  Kill the code it is long past due.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 2bd9805..86ebf02 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -98,7 +98,6 @@
 #ifdef SOCK_REFCNT_DEBUG
 	pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
 #endif
-	release_net(twsk_net(tw));
 	kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
 	module_put(owner);
 }
@@ -196,7 +195,7 @@
 		tw->tw_transparent  = inet->transparent;
 		tw->tw_prot	    = sk->sk_prot_creator;
 		atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
-		twsk_net_set(tw, hold_net(sock_net(sk)));
+		twsk_net_set(tw, sock_net(sk));
 		/*
 		 * Because we use RCU lookups, we should not set tw_refcnt
 		 * to a non null value before everything is setup for this