Document kern.log_wakeups_per_second.

PR:		148680
MFC after:	2 weeks

Author: bsdjhb

sys/kern/subr_log.c

@@ -98,10 +98,10 @@ static struct cv	log_wakeup;
 struct mtx		msgbuf_lock;
 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
 
-/* Times per second to check for a pending syslog wakeup. */
 static int	log_wakeups_per_second = 5;
 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
-    &log_wakeups_per_second, 0, "");
+    &log_wakeups_per_second, 0,
+    "How often (times per second) to check for /dev/log waiters.");
 
 /*ARGSUSED*/
 static	int