tcp: rearrange enum and remove unused variable

Rearrange the enum tt_which such that TT_REXMIT is 0. This allows
an extension of the BBLog event RTO in a backwards compatible way.
Remove tcptimers, which was only used in trpt, a utility removed
from the source tree recently.

Reviewed by:		glebius@, guest-ccui@
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D38547

sys/netinet/tcp_timer.h

@@ -127,11 +127,6 @@
  */
 #define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4)
 
-#ifdef	TCPTIMERS
-static const char *tcptimers[] =
-    { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" };
-#endif
-
 /*
  * Force a time value to be in a certain range.
  */

sys/netinet/tcp_var.h

@@ -127,11 +127,11 @@ struct sackhint {
 STAILQ_HEAD(tcp_log_stailq, tcp_log_mem);
 
 typedef enum {
-	TT_DELACK = 0,
-	TT_REXMT,
+	TT_REXMT = 0,
 	TT_PERSIST,
 	TT_KEEP,
 	TT_2MSL,
+	TT_DELACK,
 	TT_N,
 } tt_which;