pkt_sched: remove unnecessary xchg() in packet schedulers

The use of xchg() hasn't been necessary since 2.2.something when proper
locking was added to packet schedulers.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 3cbc3ff..f840d6b 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -331,10 +331,9 @@
 	root_lock = qdisc_root_sleeping_lock(sch);
 
 	spin_lock_bh(root_lock);
-	d = xchg(&q->delay_dist, d);
+	kfree(q->delay_dist);
+	q->delay_dist = d;
 	spin_unlock_bh(root_lock);
-
-	kfree(d);
 	return 0;
 }