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>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -279,6 +279,11 @@ 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;
+
 	size_t num_ports;
 };