firmware: efi: Switch to sys-off handler

Use sys-off handler that replaces global pm_power_off variable and allows
to register multiple power-off handlers.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

drivers/firmware/efi/reboot.c

@@ -6,8 +6,6 @@
 #include <linux/efi.h>
 #include <linux/reboot.h>
 
-static void (*orig_pm_power_off)(void);
-
 int efi_reboot_quirk_mode = -1;
 
 void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
@@ -51,26 +49,28 @@ bool __weak efi_poweroff_required(void)
 	return false;
 }
 
-static void efi_power_off(void)
+static void efi_power_off(struct power_off_data *data)
 {
 	efi.reset_system(EFI_RESET_SHUTDOWN, EFI_SUCCESS, 0, NULL);
 	/*
 	 * The above call should not return, if it does fall back to
 	 * the original power off method (typically ACPI poweroff).
 	 */
-	if (orig_pm_power_off)
-		orig_pm_power_off();
 }
 
+static struct sys_off_handler efi_sys_off = {
+	.power_off_priority = POWEROFF_PRIO_FIRMWARE + 1,
+	.power_off_chaining_allowed = true,
+	.power_off_cb = efi_power_off,
+};
+
 static int __init efi_shutdown_init(void)
 {
 	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_RESET_SYSTEM))
 		return -ENODEV;
 
-	if (efi_poweroff_required()) {
-		orig_pm_power_off = pm_power_off;
-		pm_power_off = efi_power_off;
-	}
+	if (efi_poweroff_required())
+		register_sys_off_handler(&efi_sys_off);
 
 	return 0;
 }