net: dsa: mv88e6xxx: SERDES support 2500BaseT via external PHY

By using an external PHY, ports 9 and 10 can support 2500BaseT.
So set this link mode in the mask when validating.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -647,8 +647,10 @@ static void mv88e6390_phylink_validate(struct mv88e6xxx_chip *chip, int port,
 				       unsigned long *mask,
 				       struct phylink_link_state *state)
 {
-	if (port >= 9)
+	if (port >= 9) {
 		phylink_set(mask, 2500baseX_Full);
+		phylink_set(mask, 2500baseT_Full);
+	}
 
 	/* No ethtool bits for 200Mbps */
 	phylink_set(mask, 1000baseT_Full);