net: ethernet: dwmac: Fix an error code in imx_dwmac_probe()

The code is return PTR_ERR(NULL) which is zero or success.  We should
return -ENOMEM instead.

Fixes: 94abdad6 ("net: ethernet: dwmac: add ethernet glue logic for NXP imx8 chip")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NFugang Duan <fugang.duan@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c

@@ -225,7 +225,7 @@ static int imx_dwmac_probe(struct platform_device *pdev)
 
 	dwmac = devm_kzalloc(&pdev->dev, sizeof(*dwmac), GFP_KERNEL);
 	if (!dwmac)
-		return PTR_ERR(dwmac);
+		return -ENOMEM;
 
 	plat_dat = stmmac_probe_config_dt(pdev, &stmmac_res.mac);
 	if (IS_ERR(plat_dat))