net: lan966x: Extend lan966x with RGMII support

Extend lan966x with RGMII support. The MAC supports all RGMII_* modes.

Signed-off-by: Horatiu Vultur <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

···
 	port->phylink_config.mac_capabilities = MAC_ASYM_PAUSE | MAC_SYM_PAUSE |
 		MAC_10 | MAC_100 | MAC_1000FD | MAC_2500FD;
 
+	phy_interface_set_rgmii(port->phylink_config.supported_interfaces);
 	__set_bit(PHY_INTERFACE_MODE_MII,
 		  port->phylink_config.supported_interfaces);
 	__set_bit(PHY_INTERFACE_MODE_GMII,

drivers/net/ethernet/microchip/lan966x/lan966x_phylink.c

···
 	port_config->pause |= tx_pause ? MLO_PAUSE_TX : 0;
 	port_config->pause |= rx_pause ? MLO_PAUSE_RX : 0;
 
+	if (phy_interface_mode_is_rgmii(interface))
+		phy_set_speed(port->serdes, speed);
+
 	lan966x_port_config_up(port);
 }