ACPI / battery: Fix acpi_battery_exit on acpi_battery_init_async errors

The acpi_lock_battery_dir() / acpi_bus_register_driver() calls in
acpi_battery_init_async() may fail.

Check that they succeeded before undoing them.

Signed-off-by: Hans de Goede <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/battery.c

···
 MODULE_LICENSE("GPL");
 
 static async_cookie_t async_cookie;
+static bool battery_driver_registered;
 static int battery_bix_broken_package;
 static int battery_notification_delay_ms;
 static unsigned int cache_time = 1000;
···
 	if (result < 0)
 		acpi_unlock_battery_dir(acpi_battery_dir);
 #endif
+	battery_driver_registered = (result == 0);
 }
 
 static int __init acpi_battery_init(void)
···
 static void __exit acpi_battery_exit(void)
 {
 	async_synchronize_cookie(async_cookie + 1);
-	acpi_bus_unregister_driver(&acpi_battery_driver);
+	if (battery_driver_registered)
+		acpi_bus_unregister_driver(&acpi_battery_driver);
 #ifdef CONFIG_ACPI_PROCFS_POWER
-	acpi_unlock_battery_dir(acpi_battery_dir);
+	if (acpi_battery_dir)
+		acpi_unlock_battery_dir(acpi_battery_dir);
 #endif
 }