ACPI: AC: Use string_choices API instead of ternary operator

Use modern string_choices API instead of manually determining the
output using ternary operator.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: mwilczy

drivers/acpi/ac.c

@@ -17,6 +17,7 @@
 #include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/power_supply.h>
+#include <linux/string_choices.h>
 #include <linux/acpi.h>
 #include <acpi/battery.h>
 
@@ -243,8 +244,8 @@ static int acpi_ac_add(struct acpi_device *device)
 		goto err_release_ac;
 	}
 
-	pr_info("%s [%s] (%s)\n", acpi_device_name(device),
-		acpi_device_bid(device), ac->state ? "on-line" : "off-line");
+	pr_info("%s [%s] (%s-line)\n", acpi_device_name(device),
+		acpi_device_bid(device), str_on_off(ac->state));
 
 	ac->battery_nb.notifier_call = acpi_ac_battery_notify;
 	register_acpi_notifier(&ac->battery_nb);