tcp: initialize variable ecn_ok in syncookies path

Using a gcc 4.4.3, warnings are emitted for a possibly uninitialized use
of ecn_ok.

This can happen if cookie_check_timestamp() returns due to not having
seen a timestamp.  Defaulting to ecn off seems like a reasonable thing
to do in this case, so initialized ecn_ok to false.
Signed-off-by: NMike Waychison <mikew@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/syncookies.c

@@ -276,7 +276,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 	int mss;
 	struct rtable *rt;
 	__u8 rcv_wscale;
-	bool ecn_ok;
+	bool ecn_ok = false;
 
 	if (!sysctl_tcp_syncookies || !th->ack || th->rst)
 		goto out;

net/ipv6/syncookies.c

@@ -165,7 +165,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	int mss;
 	struct dst_entry *dst;
 	__u8 rcv_wscale;
-	bool ecn_ok;
+	bool ecn_ok = false;
 
 	if (!sysctl_tcp_syncookies || !th->ack || th->rst)
 		goto out;