net: dsa: mt7530: use resolved link config in mac_link_up()

Convert the mt7530 switch driver to use the finalised link
parameters in mac_link_up() rather than the parameters in mac_config().

Signed-off-by: René van Dorst <opensource@vdorst.com>
Tested-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>