tcp: minor optimization around tcp_hdr() usage in receive path

This is additional to the
commit ea1627c20c34 ("tcp: minor optimizations around tcp_hdr() usage").
At this point, skb->data is same with tcp_hdr() as tcp header has not
been pulled yet. So use the less expensive one to get the tcp header.

Remove the third parameter of tcp_rcv_established() and put it into
the function body.

Furthermore, the local variables are listed as a reverse christmas tree :)

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.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 1191cac..d5ffb57 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5390,11 +5390,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
  *	the rest is checked inline. Fast processing is turned on in
  *	tcp_data_queue when everything is OK.
  */
-void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
-			 const struct tcphdr *th)
+void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 {
-	unsigned int len = skb->len;
+	const struct tcphdr *th = (const struct tcphdr *)skb->data;
 	struct tcp_sock *tp = tcp_sk(sk);
+	unsigned int len = skb->len;
 
 	/* TCP congestion window tracking */
 	trace_tcp_probe(sk, skb);