ramips: do not print error log when mdio bus is disabled

The mdio bus is used to control externel switch. In most cases, they are
disabled, which is the normal behavior. Treating this as an error makes
no sense, so we need to change the notification level from error to info.

Fixes: a2acdf9607 ("ramips: mt7620: remove useless GMAC nodes")
Signed-off-by: Shiji Yang <yangshiji66@qq.com>
(cherry picked from commit 285f0668f4)

target/linux/ramips/files/drivers/net/ethernet/ralink/mdio.c

@@ -257,7 +257,7 @@ err_free_bus:
 err_put_node:
 	of_node_put(mii_np);
 err_no_bus:
-	dev_err(priv->dev, "%s disabled", "mdio-bus");
+	dev_info(priv->dev, "%s disabled", "mdio-bus");
 	priv->mii_bus = NULL;
 	return err;
 }