[ACPI] ACPI poweroff fix

Register an "acpi" system device to be notified of shutdown preparation.
This depends on CONFIG_PM

http://bugzilla.kernel.org/show_bug.cgi?id=4041

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/linux/pm.h b/include/linux/pm.h
index ed2b76e..da88851 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -175,7 +175,7 @@
 };
 
 extern void pm_set_ops(struct pm_ops *);
-
+extern struct pm_ops *pm_ops;
 extern int pm_suspend(suspend_state_t state);