net: dsa: tag_lan9303: let DSA core deal with TX reallocation

Now that we have a central TX reallocation procedure that accounts for
the tagger's needed headroom in a generic way, we can remove the
skb_cow_head call.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/dsa/tag_lan9303.c

@@ -58,15 +58,6 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
 	__be16 *lan9303_tag;
 	u16 tag;
 
-	/* insert a special VLAN tag between the MAC addresses
-	 * and the current ethertype field.
-	 */
-	if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
-		dev_dbg(&dev->dev,
-			"Cannot make room for the special tag. Dropping packet\n");
-		return NULL;
-	}
-
 	/* provide 'LAN9303_TAG_LEN' bytes additional space */
 	skb_push(skb, LAN9303_TAG_LEN);