net: dsa: Move the phylink driver calls into port.c

In order to have a common handling of PHYLINK for the slave and non-user
ports, the DSA core glue logic (between PHYLINK and the driver) must use
an API that does not rely on a struct net_device.

These will also be called by the CPU-port-handling code in a further
patch.

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