net: mdio-ipq4019: add missing error check

If an optional resource is found but fails to remap, return on failure.
Avoids any potential problems when using the iomapped resource as the
assumption is that it's available.

Fixes: 23a890d493e3 ("net: mdio: Add the reset function for IPQ MDIO driver")
Signed-off-by: Rosen Penev <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/mdio/mdio-ipq4019.c

···
 	/* The platform resource is provided on the chipset IPQ5018 */
 	/* This resource is optional */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
-	if (res)
+	if (res) {
 		priv->eth_ldo_rdy = devm_ioremap_resource(&pdev->dev, res);
+		if (IS_ERR(priv->eth_ldo_rdy))
+			return PTR_ERR(priv->eth_ldo_rdy);
+	}
 
 	bus->name = "ipq4019_mdio";
 	bus->read = ipq4019_mdio_read_c22;