sch_htb: fix doc warning in htb_activate()

Add description for parameters of htb_activate()
to fix gcc W=1 warnings:

net/sched/sch_htb.c:562: warning: Function parameter or member 'q' not described in 'htb_activate'
net/sched/sch_htb.c:562: warning: Function parameter or member 'cl' not described in 'htb_activate'
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_htb.c

@@ -575,6 +575,8 @@ htb_change_class_mode(struct htb_sched *q, struct htb_class *cl, s64 *diff)
 
 /**
  * htb_activate - inserts leaf cl into appropriate active feeds
+ * @q: the priority event queue
+ * @cl: the target class
  *
  * Routine learns (new) priority of leaf and activates feed chain
  * for the prio. It can be called on already active leaf safely.