net: dsa: mv88e6xxx: remove port_link_state functions

The port_link_state method is only used by mv88e6xxx_port_setup_mac(),
which is now only called during port setup, rather than also being
called via phylink's mac_config method.

Remove this now unnecessary optimisation, which allows us to remove the
port_link_state methods as well.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>