net: dsa: tag_mtk: use the generic flow dissector procedure

Remove the .flow_dissect procedure, so the flow dissector will call the
generic variant which works for this tagging protocol.

Cc: DENG Qingfang <dqfext@gmail.com>
Cc: Sean Wang <sean.wang@mediatek.com>
Cc: John Crispin <john@phrozen.org>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/tag_mtk.c

@@ -105,19 +105,11 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	return skb;
 }
 
-static void mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
-				 int *offset)
-{
-	*offset = 4;
-	*proto = ((__be16 *)skb->data)[1];
-}
-
 static const struct dsa_device_ops mtk_netdev_ops = {
 	.name		= "mtk",
 	.proto		= DSA_TAG_PROTO_MTK,
 	.xmit		= mtk_tag_xmit,
 	.rcv		= mtk_tag_rcv,
-	.flow_dissect	= mtk_tag_flow_dissect,
 	.overhead	= MTK_HDR_LEN,
 };