packet: report tx_dropped in packet_direct_xmit

Since commit 015f0688 ("net: net: add a core netdev->tx_dropped
counter"), we can now account for TX drops from within the core
stack instead of drivers.

Therefore, fix packet_direct_xmit() and increase drop count when we
encounter a problem before driver's xmit function was called (we do
not want to doubly account for it).
Suggested-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -275,6 +275,7 @@ static int packet_direct_xmit(struct sk_buff *skb)
 
 	return ret;
 drop:
+	atomic_long_inc(&dev->tx_dropped);
 	kfree_skb(skb);
 	return NET_XMIT_DROP;
 }