net: dsa: Use PHYLINK for the CPU/DSA ports

For DSA switches that do not have an .adjust_link callback, aka those
who transitioned totally to the PHYLINK-compliant API, use PHYLINK to
drive the CPU/DSA ports.

The PHYLIB usage and .adjust_link are kept but deprecated, and users are
asked to transition from it.  The reason why we can't do anything for
them is because PHYLINK does not wrap the fixed-link state behind a
phydev object, so we cannot wrap .phylink_mac_config into .adjust_link
unless we fabricate a phy_device structure.

For these ports, the newly introduced PHYLINK_DEV operation type is
used and the dsa_switch device structure is passed to PHYLINK for
printing purposes.  The handling of the PHYLINK_NETDEV and PHYLINK_DEV
PHYLINK instances is common from the perspective of the driver.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>