tcp: shrink tcp_timewait_sock by 8 bytes

Reducing tcp_timewait_sock from 280 bytes to 272 bytes
allows SLAB to pack 15 objects per page instead of 14 (on x86)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -229,6 +229,7 @@ struct sock_common {
 	union {
 		int		skc_incoming_cpu;
 		u32		skc_rcv_wnd;
+		u32		skc_tw_rcv_nxt; /* struct tcp_timewait_sock  */
 	};
 
 	atomic_t		skc_refcnt;
@@ -237,6 +238,7 @@ struct sock_common {
 	union {
 		u32		skc_rxhash;
 		u32		skc_window_clamp;
+		u32		skc_tw_snd_nxt; /* struct tcp_timewait_sock */
 	};
 	/* public: */
 };