ACPI / fan: Make struct dev_pm_ops const

Silence the following checkpatch warning:
WARNING: struct dev_pm_ops should normally be const.

Signed-off-by: Kaiyen Chang <[e-mail]>
Signed-off-by: Brian Norris <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/fan.c

···
 #ifdef CONFIG_PM_SLEEP
 static int acpi_fan_suspend(struct device *dev);
 static int acpi_fan_resume(struct device *dev);
-static struct dev_pm_ops acpi_fan_pm = {
+static const struct dev_pm_ops acpi_fan_pm = {
 	.resume = acpi_fan_resume,
 	.freeze = acpi_fan_suspend,
 	.thaw = acpi_fan_resume,