net: dsa: Pass pcs_poll flag from driver to PHYLINK

The DSA drivers that implement .phylink_mac_link_state should normally
register an interrupt for the PCS, from which they should call
phylink_mac_change(). However not all switches implement this, and those
who don't should set this flag in dsa_switch in the .setup callback, so
that PHYLINK will poll for a few ms until the in-band AN link timer
expires and the PCS state settles.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Conflicts:
	include/net/dsa.h

trivially with upstream commit 05f294a85235 ("net: dsa: allocate ports
on touch") which was merged in v5.4-rc3.

(cherry picked from commit 222d888331)

include/net/dsa.h

@@ -277,6 +277,11 @@ struct dsa_switch {
 	 */
 	bool			vlan_filtering;
 
+	/* MAC PCS does not provide link state change interrupt, and requires
+	 * polling. Flag passed on to PHYLINK.
+	 */
+	bool			pcs_poll;
+
 	/* Dynamically allocated ports, keep last */
 	size_t num_ports;
 	struct dsa_port ports[];

net/dsa/port.c

@@ -601,6 +601,7 @@ static int dsa_port_phylink_register(struct dsa_port *dp)
 
 	dp->pl_config.dev = ds->dev;
 	dp->pl_config.type = PHYLINK_DEV;
+	dp->pl_config.pcs_poll = ds->pcs_poll;
 
 	dp->pl = phylink_create(&dp->pl_config, of_fwnode_handle(port_dn),
 				mode, &dsa_port_phylink_mac_ops);