net_sched: fix a missing idr_remove() in u32_delete_key()

When we delete a u32 key via u32_delete_key(), we forget to
call idr_remove() to remove its handle from IDR.

Fixes: e7614370 ("net_sched: use idr to allocate u32 filter handles")
Reported-by: NMarcin Kabiesz <admin@hostcenter.eu>
Tested-by: NMarcin Kabiesz <admin@hostcenter.eu>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/cls_u32.c

@@ -489,6 +489,7 @@ static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
 				RCU_INIT_POINTER(*kp, key->next);
 
 				tcf_unbind_filter(tp, &key->res);
+				idr_remove(&ht->handle_idr, key->handle);
 				tcf_exts_get_net(&key->exts);
 				call_rcu(&key->rcu, u32_delete_key_freepf_rcu);
 				return 0;