pkt_sched: Fix unlocking in tc_ctl_tfilter()

Fix a bug with spin_lock_bh() inserted instead of spin_unlock_bh() by
some recent patch. 
Reported-by: NDenys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: NJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -280,7 +280,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
 		if (n->nlmsg_type == RTM_DELTFILTER && t->tcm_handle == 0) {
 			spin_lock_bh(root_lock);
 			*back = tp->next;
-			spin_lock_bh(root_lock);
+			spin_unlock_bh(root_lock);
 
 			tfilter_notify(skb, n, tp, fh, RTM_DELTFILTER);
 			tcf_destroy(tp);