net: enetc: Use DT protocol information to set up the ports

Use DT information rather than in-band information from bootloader to
set up MAC for XGMII. For RGMII use the DT indication in addition to
RGMII defaults in hardware.
However, this implies that PHY connection information needs to be
extracted before netdevice creation, when the ENETC Port MAC is
being configured.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>