net: dsa: sja1105: Mark in-band AN modes not supported for PHYLINK

We need a better way to signal this, perhaps in phylink_validate, but
for now just print this error message as guidance for other people
looking at this driver's code while trying to rework PHYLINK.

Cc: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -806,6 +806,11 @@ static void sja1105_mac_config(struct dsa_switch *ds, int port,
 	if (sja1105_phy_mode_mismatch(priv, port, state->interface))
 		return;
 
+	if (link_an_mode == MLO_AN_INBAND) {
+		dev_err(ds->dev, "In-band AN not supported!\n");
+		return;
+	}
+
 	sja1105_adjust_port_config(priv, port, state->speed);
 }