net: dsa: mv88e6xxx: simulate Amethyst PHY model number

Amethyst internal PHYs also report empty model number in MII_PHYSID2.

Fill in switch product number, as is done for Topaz and Peridot.
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -3165,6 +3165,7 @@ static int mv88e6xxx_setup(struct dsa_switch *ds)
 static const u16 family_prod_id_table[] = {
 	[MV88E6XXX_FAMILY_6341] = MV88E6XXX_PORT_SWITCH_ID_PROD_6341,
 	[MV88E6XXX_FAMILY_6390] = MV88E6XXX_PORT_SWITCH_ID_PROD_6390,
+	[MV88E6XXX_FAMILY_6393] = MV88E6XXX_PORT_SWITCH_ID_PROD_6393X,
 };
 
 static int mv88e6xxx_mdio_read(struct mii_bus *bus, int phy, int reg)