watchdog: wdat_wdt: fix return value check in wdat_wdt_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().
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/watchdog/wdat_wdt.c

@@ -351,16 +351,17 @@ static int wdat_wdt_probe(struct platform_device *pdev)
 		res = &pdev->resource[i];
 		if (resource_type(res) == IORESOURCE_MEM) {
 			reg = devm_ioremap_resource(&pdev->dev, res);
+			if (IS_ERR(reg))
+				return PTR_ERR(reg);
 		} else if (resource_type(res) == IORESOURCE_IO) {
 			reg = devm_ioport_map(&pdev->dev, res->start, 1);
+			if (!reg)
+				return -ENOMEM;
 		} else {
 			dev_err(&pdev->dev, "Unsupported resource\n");
 			return -EINVAL;
 		}
 
-		if (!reg)
-			return -ENOMEM;
-
 		regs[i] = reg;
 	}