staging: mt7621-eth: fix return value check in mt7621_gsw_probe()

In case of error, the function devm_ioremap_resource() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR().

Fixes: f079b6406348 ("staging: mt7621-eth: add gigabit switch driver (GSW)")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

target/linux/ramips/files-4.14/drivers/net/ethernet/mtk/esw_rt3050.c

@@ -1358,8 +1358,8 @@ static int esw_probe(struct platform_device *pdev)
 	esw->dev = &pdev->dev;
 	esw->irq = irq_of_parse_and_map(np, 0);
 	esw->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!esw->base)
-		return -EADDRNOTAVAIL;
+	if (IS_ERR(esw->base))
+		return PTR_ERR(esw->base);
 
 	port_map = of_get_property(np, "mediatek,portmap", NULL);
 	if (port_map)

target/linux/ramips/files-4.14/drivers/net/ethernet/mtk/gsw_mt7620.c

@@ -215,8 +215,8 @@ static int mt7620_gsw_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	gsw->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!gsw->base)
-		return -EADDRNOTAVAIL;
+	if (IS_ERR(gsw->base))
+		return PTR_ERR(gsw->base);
 
 	gsw->dev = &pdev->dev;
 

target/linux/ramips/files-4.14/drivers/net/ethernet/mtk/gsw_mt7621.c

@@ -245,8 +245,8 @@ static int mt7621_gsw_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	gsw->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!gsw->base)
-		return -EADDRNOTAVAIL;
+	if (IS_ERR(gsw->base))
+		return PTR_ERR(gsw->base);
 
 	gsw->dev = &pdev->dev;
 	gsw->irq = platform_get_irq(pdev, 0);