Revert "net: dsa: Allow drivers to filter packets they can decode source port from"

This reverts commit cc1939e4b3.

Currently 2 classes of DSA drivers are able to send/receive packets
directly through the DSA master:
- drivers with DSA_TAG_PROTO_NONE
- sja1105

Now that sja1105 has gained the ability to perform traffic termination
even under the tricky case (VLAN-aware bridge), and that is much more
functional (we can perform VLAN-aware bridging with foreign interfaces),
there is no reason to keep this code in the receive path of the network
core. So delete it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ethernet/eth.c

@@ -182,12 +182,8 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
 	 * at all, so we check here whether one of those tagging
 	 * variants has been configured on the receiving interface,
 	 * and if so, set skb->protocol without looking at the packet.
-	 * The DSA tagging protocol may be able to decode some but not all
-	 * traffic (for example only for management). In that case give it the
-	 * option to filter the packets from which it can decode source port
-	 * information.
 	 */
-	if (unlikely(netdev_uses_dsa(dev)) && dsa_can_decode(skb, dev))
+	if (unlikely(netdev_uses_dsa(dev)))
 		return htons(ETH_P_XDSA);
 
 	if (likely(eth_proto_is_802_3(eth->h_proto)))