net: sched: sch: add extack to change class

This patch adds extack support for class change callback api. This prepares
to handle extack support inside each specific class implementation.

Cc: David Ahern <dsahern@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_htb.c

@@ -1327,7 +1327,7 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
 
 static int htb_change_class(struct Qdisc *sch, u32 classid,
 			    u32 parentid, struct nlattr **tca,
-			    unsigned long *arg)
+			    unsigned long *arg, struct netlink_ext_ack *extack)
 {
 	int err = -EINVAL;
 	struct htb_sched *q = qdisc_priv(sch);