net-tcp: retire TFO_SERVER_WO_SOCKOPT2 config

TFO_SERVER_WO_SOCKOPT2 was intended for debugging purposes during
Fast Open development. Remove this config option and also
update/clean-up the documentation of the Fast Open sysctl.

Reported-by: Piotr Jurkiewicz <piotr.jerzy.jurkiewicz@gmail.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index c00e7d5..25d64f6 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -227,10 +227,9 @@
 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
 
 /* Force enable TFO on all listeners, i.e., not requiring the
- * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
+ * TCP_FASTOPEN socket option.
  */
 #define	TFO_SERVER_WO_SOCKOPT1	0x400
-#define	TFO_SERVER_WO_SOCKOPT2	0x800
 
 extern struct inet_timewait_death_row tcp_death_row;