net: dsa: tag_ar9331: 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.

Cc: Per Forlin <per.forlin@axis.com>
Cc: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Oleksij Rempel <linux@rempel-privat.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/dsa/tag_ar9331.c

@@ -31,9 +31,6 @@ static struct sk_buff *ar9331_tag_xmit(struct sk_buff *skb,
 	__le16 *phdr;
 	u16 hdr;
 
-	if (skb_cow_head(skb, AR9331_HDR_LEN) < 0)
-		return NULL;
-
 	phdr = skb_push(skb, AR9331_HDR_LEN);
 
 	hdr = FIELD_PREP(AR9331_HDR_VERSION_MASK, AR9331_HDR_VERSION);