Fixed a buffer overrun. In my kernel configuration, tcp_syncache happens

to be followed by nfsnodehashtbl, so bzeroing callouts beyond the end of
tcp_syncache soon caused a null pointer panic when nfsnodehashtbl was
accessed.

sys/netinet/tcp_syncache.c

@@ -237,7 +237,7 @@ syncache_init(void)
 	}
 
 	/* Initialize the timer queues. */
-	for (i = 0; i <= TCP_MAXRXTSHIFT; i++) {
+	for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
 		TAILQ_INIT(&tcp_syncache.timerq[i]);
 		callout_init(&tcp_syncache.tt_timerq[i], 0);
 	}