net: stmmac: Fix error return code in ingenic_mac_probe()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 2bb4b98b ("net: stmmac: Add Ingenic SoCs MAC support.")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -263,6 +263,7 @@ static int ingenic_mac_probe(struct platform_device *pdev)
 	mac->regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, "mode-reg");
 	if (IS_ERR(mac->regmap)) {
 		dev_err(&pdev->dev, "%s: Failed to get syscon regmap\n", __func__);
+		ret = PTR_ERR(mac->regmap);
 		goto err_remove_config_dt;
 	}