phy: add driver for Intel XWAY PHY

Add a driver for the Intel XWAY GbE PHY:
 - configure RGMII using dt phy-mode and standard delay properties
 - use genphy_config

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

include/phy.h

@@ -380,6 +380,7 @@ int phy_teranetics_init(void);
 int phy_ti_init(void);
 int phy_vitesse_init(void);
 int phy_xilinx_init(void);
+int phy_xway_init(void);
 int phy_mscc_init(void);
 int phy_fixed_init(void);
 int phy_ncsi_init(void);