ipv4: be friend with drop monitor

Replace some dev_kfree_skb() with kfree_skb() calls when
we drop one skb, this might help bug tracking.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e560ef3..e7a92fd 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -278,7 +278,7 @@
 	return NETDEV_TX_OK;
 
 free_skb:
-	dev_kfree_skb(skb);
+	kfree_skb(skb);
 out:
 	dev->stats.tx_dropped++;
 	return NETDEV_TX_OK;
@@ -301,7 +301,7 @@
 	return NETDEV_TX_OK;
 
 free_skb:
-	dev_kfree_skb(skb);
+	kfree_skb(skb);
 out:
 	dev->stats.tx_dropped++;
 	return NETDEV_TX_OK;