net: add skb_get_tx_queue() helper

Replace occurences of skb_get_queue_mapping() and follow-up
netdev_get_tx_queue() with an actual helper function.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index a5ad068..12b1df9 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -115,7 +115,7 @@
 			continue;
 		}
 
-		txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
+		txq = skb_get_tx_queue(dev, skb);
 
 		local_irq_save(flags);
 		HARD_TX_LOCK(dev, txq, smp_processor_id());