net: dsa: mt7530: sort link settings ops and force link down on all ports

port_enable and port_disable clears the link settings. Move that to
mt7530_setup() and mt7531_setup_common() which set up the switches. This
way, the link settings are cleared on all ports at setup, and then only
once with phylink_mac_link_down() when a link goes down.

Enable force mode at setup to apply the force part of the link settings.
This ensures that disabled ports will have their link down.

Suggested-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>