[TCP]: Fix some warning when MD5 is disabled.

Just some mis-placed ifdefs:

net/ipv4/tcp_minisocks.c: In function ‘tcp_twsk_destructor’:
net/ipv4/tcp_minisocks.c:364: warning: unused variable ‘twsk’
net/ipv6/tcp_ipv6.c:1846: warning: ‘tcp_sock_ipv6_specific’ defined but not used
net/ipv6/tcp_ipv6.c:1877: warning: ‘tcp_sock_ipv6_mapped_specific’ defined but not used

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index ac55d88..4a0ee90 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -361,8 +361,8 @@
 
 void tcp_twsk_destructor(struct sock *sk)
 {
-	struct tcp_timewait_sock *twsk = tcp_twsk(sk);
 #ifdef CONFIG_TCP_MD5SIG
+	struct tcp_timewait_sock *twsk = tcp_twsk(sk);
 	if (twsk->tw_md5_keylen)
 		tcp_put_md5sig_pool();
 #endif