regulator: stm32-pwr: Fix return value check in stm32_pwr_regulator_probe()

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

Fixes: 6cdae8173f67 ("regulator: Add support for stm32 power regulators")
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/stm32-pwr.c

···
 	int i, ret = 0;
 
 	base = of_iomap(np, 0);
-	if (IS_ERR(base)) {
+	if (!base) {
 		dev_err(&pdev->dev, "Unable to map IO memory\n");
-		return PTR_ERR(base);
+		return -ENOMEM;
 	}
 
 	config.dev = &pdev->dev;