watchdog: jz4740: Fix return value check in jz4740_wdt_probe()

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

Fixes: 6d532143 ("watchdog: jz4740: Use regmap provided by TCU driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20210304045909.945799-1-weiyongjun1@huawei.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/jz4740_wdt.c

@@ -176,9 +176,9 @@ static int jz4740_wdt_probe(struct platform_device *pdev)
 	watchdog_set_drvdata(jz4740_wdt, drvdata);
 
 	drvdata->map = device_node_to_regmap(dev->parent->of_node);
-	if (!drvdata->map) {
+	if (IS_ERR(drvdata->map)) {
 		dev_err(dev, "regmap not found\n");
-		return -EINVAL;
+		return PTR_ERR(drvdata->map);
 	}
 
 	return devm_watchdog_register_device(dev, &drvdata->wdt);