Fix ThinkPad T42 poweroff failure introduced by by "PM: Introduce pm_power_off_prepare"

Commit bd804eba1c8597cbb7cd5a5f9fe886aae16a079a ("PM: Introduce
pm_power_off_prepare") caused problems in the poweroff path, as reported by
YOSHIFUJI Hideaki / 吉藤英明.

Generally, sysdev_shutdown() should be called after the ACPI preparation for
powering the system off.  To make it happen, we can separate sysdev_shutdown()
from device_shutdown() and call it directly wherever necessary.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 324ac01..eb72255 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -216,6 +216,7 @@
 		 * sleep state after all
 		 */
 		error = hibernation_ops->prepare();
+		sysdev_shutdown();
 		if (!error)
 			error = hibernation_ops->enter();
 	} else {