hwmon: (acpi_power_meter) Fix build warning

Commit c5dec01822 (acpi_power_meter: Use struct
dev_pm_ops for power management) introduced the following build warning. It is
seen if CONFIG_PM_SLEEP is not defined.

acpi_power_meter.c:930:12: warning: acpi_power_meter_resume defined but not used

Fix it.

Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/hwmon/acpi_power_meter.c

@@ -927,6 +927,8 @@ static int acpi_power_meter_remove(struct acpi_device *device, int type)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+
 static int acpi_power_meter_resume(struct device *dev)
 {
 	struct acpi_power_meter_resource *resource;
@@ -944,6 +946,8 @@ static int acpi_power_meter_resume(struct device *dev)
 	return 0;
 }
 
+#endif /* CONFIG_PM_SLEEP */
+
 static SIMPLE_DEV_PM_OPS(acpi_power_meter_pm, NULL, acpi_power_meter_resume);
 
 static struct acpi_driver acpi_power_meter_driver = {