dp83640: use proper function to free transmit time stamping packets

The previous commit enforces a new rule for handling the cloned packets
for transmit time stamping. These packets must not be freed using any other
function than skb_complete_tx_timestamp. This commit fixes the one and only
driver using this API.

The driver first appeared in v3.0.
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/dp83640.c

@@ -1192,7 +1192,7 @@ static void dp83640_txtstamp(struct phy_device *phydev,
 
 	case HWTSTAMP_TX_ONESTEP_SYNC:
 		if (is_sync(skb, type)) {
-			kfree_skb(skb);
+			skb_complete_tx_timestamp(skb, NULL);
 			return;
 		}
 		/* fall through */
@@ -1203,7 +1203,7 @@ static void dp83640_txtstamp(struct phy_device *phydev,
 
 	case HWTSTAMP_TX_OFF:
 	default:
-		kfree_skb(skb);
+		skb_complete_tx_timestamp(skb, NULL);
 		break;
 	}
 }