power: supply: mt6370: Fix return value check in mt6370_chg_probe()

If create_singlethread_workqueue() fails, it returns a null pointer,
replace IS_ERR() check with NULL pointer check.

Fixes: 233cb8a47d ("power: supply: mt6370: Add MediaTek MT6370 charger driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: ChiaEn Wu <chiaen_wu@richtek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/mt6370-charger.c

@@ -911,8 +911,8 @@ static int mt6370_chg_probe(struct platform_device *pdev)
 	priv->attach = MT6370_ATTACH_STAT_DETACH;
 
 	priv->wq = create_singlethread_workqueue(dev_name(priv->dev));
-	if (IS_ERR(priv->wq))
-		return dev_err_probe(dev, PTR_ERR(priv->wq),
+	if (!priv->wq)
+		return dev_err_probe(dev, -ENOMEM,
 				     "Failed to create workqueue\n");
 
 	ret = devm_add_action_or_reset(dev, mt6370_chg_destroy_wq, priv->wq);