net: enetc: allow phy-mode = "1000base-x"

The driver code proper is handled by the lynx_pcs. The enetc just needs
to populate phylink's supported_interfaces array, and return true for
this phy-mode in enetc_port_has_pcs(), such that it creates an internal
MDIO bus through which the Lynx PCS registers are accessed.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20240103113445.3892971-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/freescale/enetc/enetc_pf.c

@@ -920,6 +920,7 @@ static void enetc_imdio_remove(struct enetc_pf *pf)
 static bool enetc_port_has_pcs(struct enetc_pf *pf)
 {
 	return (pf->if_mode == PHY_INTERFACE_MODE_SGMII ||
+		pf->if_mode == PHY_INTERFACE_MODE_1000BASEX ||
 		pf->if_mode == PHY_INTERFACE_MODE_2500BASEX ||
 		pf->if_mode == PHY_INTERFACE_MODE_USXGMII);
 }
@@ -1116,6 +1117,8 @@ static int enetc_phylink_create(struct enetc_ndev_priv *priv,
 		  pf->phylink_config.supported_interfaces);
 	__set_bit(PHY_INTERFACE_MODE_SGMII,
 		  pf->phylink_config.supported_interfaces);
+	__set_bit(PHY_INTERFACE_MODE_1000BASEX,
+		  pf->phylink_config.supported_interfaces);
 	__set_bit(PHY_INTERFACE_MODE_2500BASEX,
 		  pf->phylink_config.supported_interfaces);
 	__set_bit(PHY_INTERFACE_MODE_USXGMII,