drivers: net: use skb_headlen()

replaces (skb->len - skb->data_len) occurrences by skb_headlen(skb)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index 1bd581e..5f70c43 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -4132,7 +4132,7 @@
 	unsigned int max_per_txd = E1000_MAX_PER_TXD;
 	unsigned int max_txd_pwr = E1000_MAX_TXD_PWR;
 	unsigned int tx_flags = 0;
-	unsigned int len = skb->len - skb->data_len;
+	unsigned int len = skb_headlen(skb);
 	unsigned int nr_frags;
 	unsigned int mss;
 	int count = 0;
@@ -4182,7 +4182,7 @@
 				dev_kfree_skb_any(skb);
 				return NETDEV_TX_OK;
 			}
-			len = skb->len - skb->data_len;
+			len = skb_headlen(skb);
 		}
 	}