macvtap: fix tx_dropped counting error

After commit 8ffab51
(macvlan: lockless tx path), tx stat counter were converted to percpu stat
structure. So we need use to this also for tx_dropped in macvtap. Otherwise, the
management won't notice the dropping packet in macvtap tx path.

Cc: Michael S. Tsirkin <[email protected]>
Cc: Vlad Yasevich <[email protected]>
Cc: Eric Dumazet <[email protected]>
Signed-off-by: Jason Wang <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Acked-by: Vlad Yasevich <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

drivers/net/macvtap.c

@@ -744,7 +744,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 	rcu_read_lock();
 	vlan = rcu_dereference(q->vlan);
 	if (vlan)
-		vlan->dev->stats.tx_dropped++;
+		this_cpu_inc(vlan->pcpu_stats->tx_dropped);
 	rcu_read_unlock();
 
 	return err;