inet: move ir_mark to fill a hole

On 64bit arches, we can save 8 bytes in inet_request_sock
by moving ir_mark to fill a hole.

While we are at it, inet_request_mark() can get a const qualifier
for listener socket.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/inet_sock.h

@@ -94,11 +94,11 @@ struct inet_request_sock {
 				acked	   : 1,
 				no_srccheck: 1;
 	kmemcheck_bitfield_end(flags);
+	u32                     ir_mark;
 	union {
 		struct ip_options_rcu	*opt;
 		struct sk_buff		*pktopts;
 	};
-	u32                     ir_mark;
 };
 
 static inline struct inet_request_sock *inet_rsk(const struct request_sock *sk)
@@ -106,13 +106,12 @@ static inline struct inet_request_sock *inet_rsk(const struct request_sock *sk)
 	return (struct inet_request_sock *)sk;
 }
 
-static inline u32 inet_request_mark(struct sock *sk, struct sk_buff *skb)
+static inline u32 inet_request_mark(const struct sock *sk, struct sk_buff *skb)
 {
-	if (!sk->sk_mark && sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept) {
+	if (!sk->sk_mark && sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept)
 		return skb->mark;
-	} else {
-		return sk->sk_mark;
-	}
+
+	return sk->sk_mark;
 }
 
 struct inet_cork {