net: enetc: kill PHY-less mode for PFs

Right now, a PHY-less port (no phy-mode, no fixed-link, no phy-handle)
doesn't register with phylink, but calls netif_carrier_on() from
enetc_start().

This makes sense for a VF, but for a PF, this is braindead, because we
never call enetc_mac_enable() so the MAC is left inoperational.
Furthermore, commit 71b77a7a ("enetc: Migrate to PHYLINK and
PCS_LYNX") put the nail in the coffin because it removed the initial
netif_carrier_off() call done right after register_netdev().

Without that call, netif_carrier_on() does not call
linkwatch_fire_event(), so the operstate remains IF_OPER_UNKNOWN.

Just deny the broken configuration by requiring that a phy-mode is
present, and always register a PF with phylink.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20220511094200.558502-1-vladimir.oltean@nxp.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>