net: dsa: remove phylink_validate() method

As of now, no DSA driver uses a custom link mode validation procedure
anymore. So remove this DSA operation and let phylink determine what is
supported based on config->mac_capabilities (if provided by the driver).
Leave a comment why we left the code that we did, and that there is more
work to do.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/dsa.h

@@ -880,9 +880,6 @@ struct dsa_switch_ops {
 	 */
 	void	(*phylink_get_caps)(struct dsa_switch *ds, int port,
 				    struct phylink_config *config);
-	void	(*phylink_validate)(struct dsa_switch *ds, int port,
-				    unsigned long *supported,
-				    struct phylink_link_state *state);
 	struct phylink_pcs *(*phylink_mac_select_pcs)(struct dsa_switch *ds,
 						      int port,
 						      phy_interface_t iface);

net/dsa/port.c

@@ -1536,16 +1536,14 @@ static void dsa_port_phylink_validate(struct phylink_config *config,
 				      unsigned long *supported,
 				      struct phylink_link_state *state)
 {
-	struct dsa_port *dp = container_of(config, struct dsa_port, pl_config);
-	struct dsa_switch *ds = dp->ds;
-
-	if (!ds->ops->phylink_validate) {
+	/* Skip call for drivers which don't yet set mac_capabilities,
+	 * since validating in that case would mean their PHY will advertise
+	 * nothing. In turn, skipping validation makes them advertise
+	 * everything that the PHY supports, so those drivers should be
+	 * converted ASAP.
+	 */
 	if (config->mac_capabilities)
 		phylink_generic_validate(config, supported, state);
-		return;
-	}
-
-	ds->ops->phylink_validate(ds, dp->index, supported, state);
 }
 
 static void dsa_port_phylink_mac_pcs_get_state(struct phylink_config *config,