mt76: fix return value check in mt76_wmac_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: c8846e10 ("mt76: add driver for MT7603E and MT7628/7688")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7603/soc.c

@@ -23,9 +23,9 @@ mt76_wmac_probe(struct platform_device *pdev)
 	}
 
 	mem_base = devm_ioremap_resource(&pdev->dev, res);
-	if (!mem_base) {
+	if (IS_ERR(mem_base)) {
 		dev_err(&pdev->dev, "Failed to get memory resource\n");
-		return -EINVAL;
+		return PTR_ERR(mem_base);
 	}
 
 	mdev = mt76_alloc_device(&pdev->dev, sizeof(*dev), &mt7603_ops,