ACPI: AC: constify powersupply properties

The array is never modified, make it const.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/ac.c

@@ -112,7 +112,7 @@ static int get_ac_property(struct power_supply *psy,
 	return 0;
 }
 
-static enum power_supply_property ac_props[] = {
+static const enum power_supply_property ac_props[] = {
 	POWER_SUPPLY_PROP_ONLINE,
 };