net: dsa: microchip: lan937x: return zero if mdio node not present

Currently, if the mdio node is not present in the dts file then
lan937x_mdio_register return -ENODEV and entire probing process fails.
To make the mdio_register generic for all ksz series switches and to
maintain back-compatibility with existing dts file, return -ENODEV is
replaced with return 0.
Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/microchip/lan937x_main.c

@@ -214,10 +214,8 @@ static int lan937x_mdio_register(struct ksz_device *dev)
 	int ret;
 
 	mdio_np = of_get_child_by_name(dev->dev->of_node, "mdio");
-	if (!mdio_np) {
-		dev_err(ds->dev, "no MDIO bus node\n");
-		return -ENODEV;
-	}
+	if (!mdio_np)
+		return 0;
 
 	bus = devm_mdiobus_alloc(ds->dev);
 	if (!bus) {