drivers: net: Remove device_node checks with of_mdiobus_register()

A number of drivers have the following pattern:

if (np)
	of_mdiobus_register()
else
	mdiobus_register()

which the implementation of of_mdiobus_register() now takes care of.
Remove that pattern in drivers that strictly adhere to it.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
Reviewed-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index ac621f4..02e8982 100644
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -450,12 +450,8 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
 	priv->slave_mii_bus->parent = ds->dev->parent;
 	priv->slave_mii_bus->phy_mask = ~priv->indir_phy_mask;
 
-	if (dn)
-		err = of_mdiobus_register(priv->slave_mii_bus, dn);
-	else
-		err = mdiobus_register(priv->slave_mii_bus);
-
-	if (err)
+	err = of_mdiobus_register(priv->slave_mii_bus, dn);
+	if (err && dn)
 		of_node_put(dn);
 
 	return err;