hwmon: (sht15) Properly handle the case CONFIG_REGULATOR=n

When CONFIG_REGULATOR isn't set, regulator_get_voltage() returns 0.
Properly handle this case by not trusting the value.

Reported-by: Jerome Oufella <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Cc: [e-mail]

drivers/hwmon/sht15.c

···
 /* If a regulator is available, query what the supply voltage actually is!*/
 	data->reg = regulator_get(data->dev, "vcc");
 	if (!IS_ERR(data->reg)) {
-		data->supply_uV = regulator_get_voltage(data->reg);
+		int voltage;
+
+		voltage = regulator_get_voltage(data->reg);
+		if (voltage)
+			data->supply_uV = voltage;
+
 		regulator_enable(data->reg);
 		/* setup a notifier block to update this if another device
 		 *  causes the voltage to change */