net: stmmac: use dev_err_probe() for reporting mdio bus registration failure

I have a board where these two lines are always printed during boot:

   imx-dwmac 30bf0000.ethernet: Cannot register the MDIO bus
   imx-dwmac 30bf0000.ethernet: stmmac_dvr_probe: MDIO bus (id: 1) registration failed

It's perfectly fine, and the device is successfully (and silently, as
far as the console goes) probed later.

Use dev_err_probe() instead, which will demote these messages to debug
level (thus removing the alarming messages from the console) when the
error is -EPROBE_DEFER, and also has the advantage of including the
error code if/when it happens to be something other than -EPROBE_DEFER.

While here, add the missing \n to one of the format strings.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20220602074840.1143360-1-linux@rasmusvillemoes.dkSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -7129,9 +7129,9 @@ int stmmac_dvr_probe(struct device *device,
 		/* MDIO bus Registration */
 		ret = stmmac_mdio_register(ndev);
 		if (ret < 0) {
-			dev_err(priv->device,
-				"%s: MDIO bus (id: %d) registration failed",
-				__func__, priv->plat->bus_id);
+			dev_err_probe(priv->device, ret,
+				      "%s: MDIO bus (id: %d) registration failed\n",
+				      __func__, priv->plat->bus_id);
 			goto error_mdio_register;
 		}
 	}

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

@@ -482,7 +482,7 @@ int stmmac_mdio_register(struct net_device *ndev)
 
 	err = of_mdiobus_register(new_bus, mdio_node);
 	if (err != 0) {
-		dev_err(dev, "Cannot register the MDIO bus\n");
+		dev_err_probe(dev, err, "Cannot register the MDIO bus\n");
 		goto bus_register_fail;
 	}