net: stmmac: platform: Fix MDIO init for platforms without PHY

The current implementation of "stmmac_dt_phy" function initializes
the MDIO platform bus data, even in the absence of PHY. This fix
will skip MDIO initialization if there is no PHY present.

Fixes: 7437127 ("net: stmmac: Convert to phylink and remove phylib logic")
Acked-by: Jayati Sahu <jayati.sahu@samsung.com>
Signed-off-by: Sriram Dash <sriram.dash@samsung.com>
Signed-off-by: Padmanabhan Rajanbabu <p.rajanbabu@samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

@@ -320,7 +320,7 @@ static int stmmac_mtl_setup(struct platform_device *pdev,
 static int stmmac_dt_phy(struct plat_stmmacenet_data *plat,
 			 struct device_node *np, struct device *dev)
 {
-	bool mdio = true;
+	bool mdio = false;
 	static const struct of_device_id need_mdio_ids[] = {
 		{ .compatible = "snps,dwc-qos-ethernet-4.10" },
 		{},