net: bcmgenet: Fix NULL vs IS_ERR() checking

The phy_attach() function does not return NULL. It returns error pointers.
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmmii.c

@@ -589,9 +589,9 @@ static int bcmgenet_mii_pd_init(struct bcmgenet_priv *priv)
 		 * Internal or external PHY with MDIO access
 		 */
 		phydev = phy_attach(priv->dev, phy_name, pd->phy_interface);
-		if (!phydev) {
+		if (IS_ERR(phydev)) {
 			dev_err(kdev, "failed to register PHY device\n");
-			return -ENODEV;
+			return PTR_ERR(phydev);
 		}
 	} else {
 		/*