net: bcmgenet: Fix return value check for fixed_phy_register()

The fixed_phy_register() function returns error pointers and never
returns NULL. Update the checks accordingly.

Fixes: b0ba512 ("net: bcmgenet: enable driver to work without a device tree")
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Acked-by: Doug Berger <opendmb@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Ruan Jinjie

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

@@ -617,7 +617,7 @@ static int bcmgenet_mii_pd_init(struct bcmgenet_priv *priv)
 		};
 
 		phydev = fixed_phy_register(PHY_POLL, &fphy_status, NULL);
-		if (!phydev || IS_ERR(phydev)) {
+		if (IS_ERR(phydev)) {
 			dev_err(kdev, "failed to register fixed PHY device\n");
 			return -ENODEV;
 		}