net: dsa/ar9331: convert to mac_link_up()

Convert the ar9331 DSA driver to use the finalised link parameters in
mac_link_up() rather than the parameters in mac_config().

Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>