regulator: rt4831: Fix return value check in rt4831_regulator_probe()

In case of error, the function dev_get_regmap() returns NULL
pointer not ERR_PTR(). The IS_ERR() test in the return value
check should be replaced with NULL test.

Fixes: 9351ab8b ("regulator: rt4831: Adds support for Richtek RT4831 DSV regulator")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210305034930.3236099-1-weiyongjun1@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/rt4831-regulator.c

@@ -153,9 +153,9 @@ static int rt4831_regulator_probe(struct platform_device *pdev)
 	int i, ret;
 
 	regmap = dev_get_regmap(pdev->dev.parent, NULL);
-	if (IS_ERR(regmap)) {
+	if (!regmap) {
 		dev_err(&pdev->dev, "Failed to init regmap\n");
-		return PTR_ERR(regmap);
+		return -ENODEV;
 	}
 
 	/* Configure DSV mode to normal by default */