net: dsa: mv88e6xxx: use link-down-define instead of plain value

Using the define here makes the code more expressive.
Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -430,7 +430,7 @@ int mv88e6xxx_port_setup_mac(struct mv88e6xxx_chip *chip, int port, int link,
 		return 0;
 
 	/* Port's MAC control must not be changed unless the link is down */
-	err = chip->info->ops->port_set_link(chip, port, 0);
+	err = chip->info->ops->port_set_link(chip, port, LINK_FORCED_DOWN);
 	if (err)
 		return err;