inet: drop prev pointer handling in request sock

When request sock are put in ehash table, the whole notion
of having a previous request to update dl_next is pointless.

Also, following patch will get rid of big purge timer,
so we want to delete a request sock without holding listener lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5b29835..082fd79 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -406,8 +406,7 @@
 					      struct sk_buff *skb,
 					      const struct tcphdr *th);
 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
-			   struct request_sock *req, struct request_sock **prev,
-			   bool fastopen);
+			   struct request_sock *req, bool fastopen);
 int tcp_child_process(struct sock *parent, struct sock *child,
 		      struct sk_buff *skb);
 void tcp_enter_loss(struct sock *sk);