regulator: gpio: properly check return value of of_get_named_gpio

The function of_get_named_gpio() could return -ENOENT, -EPROBE_DEFER
-EINVAL and so on. Currently, for the optional property "enable-gpio",
we only check -EPROBE_DEFER, this is not enough since there may be
misconfigured "enable-gpio" in the DTB, of_get_named_gpio() will return
-EINVAL in this case, we should return immediately here. And for the
optional property "gpios", we didn't check the return value, the driver
will continue to the point where gpio_request_array() is called, it
doesn't make sense to continue if we got -EPROBE_DEFER or -EINVAL here.

This patch tries to address these two issues by properly checking the
return value of of_get_named_gpio.

Signed-off-by: Jisheng Zhang <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/gpio-regulator.c

···
 	of_property_read_u32(np, "startup-delay-us", &config->startup_delay);
 
 	config->enable_gpio = of_get_named_gpio(np, "enable-gpio", 0);
-	if (config->enable_gpio == -EPROBE_DEFER)
-		return ERR_PTR(-EPROBE_DEFER);
+	if (config->enable_gpio < 0 && config->enable_gpio != -ENOENT)
+		return ERR_PTR(config->enable_gpio);
 
 	/* Fetch GPIOs. - optional property*/
 	ret = of_gpio_count(np);
···
 
 		for (i = 0; i < config->nr_gpios; i++) {
 			gpio = of_get_named_gpio(np, "gpios", i);
-			if (gpio < 0)
+			if (gpio < 0) {
+				if (gpio != -ENOENT)
+					return ERR_PTR(gpio);
 				break;
+			}
 			config->gpios[i].gpio = gpio;
 			if (proplen > 0) {
 				of_property_read_u32_index(np, "gpios-states",