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/dccp/ipv6.c b/net/dccp/ipv6.c
index 6883193..d9cc731f 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -686,7 +686,7 @@
 		if (likely(sk->sk_state == DCCP_LISTEN)) {
 			nsk = dccp_check_req(sk, skb, req);
 		} else {
-			inet_csk_reqsk_queue_drop(sk, req);
+			inet_csk_reqsk_queue_drop_and_put(sk, req);
 			goto lookup;
 		}
 		if (!nsk) {