tcp/dccp: add inet_csk_reqsk_queue_drop_and_put() helper

Let's reduce the confusion about inet_csk_reqsk_queue_drop() :
In many cases we also need to release reference on request socket,
so add a helper to do this, reducing code size and complexity.

Fixes: 4bdc3d66147b ("tcp/dccp: fix behavior of stale SYN_RECV request sockets")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 7ce1c57..acb06f8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1386,7 +1386,7 @@
 		if (likely(sk->sk_state == TCP_LISTEN)) {
 			nsk = tcp_check_req(sk, skb, req, false);
 		} else {
-			inet_csk_reqsk_queue_drop(sk, req);
+			inet_csk_reqsk_queue_drop_and_put(sk, req);
 			goto lookup;
 		}
 		if (!nsk) {