PM: ACPI and APM must not be enabled at the same time

ACPI and APM used "pm_active" to guarantee that
they would not be simultaneously active.

But pm_active was recently moved under CONFIG_PM_LEGACY,
so that without CONFIG_PM_LEGACY, pm_active became a NOP --
allowing ACPI and APM to both be simultaneously enabled.
This caused unpredictable results, including boot hangs.

Further, the code under CONFIG_PM_LEGACY is scheduled
for removal.

So replace pm_active with pm_flags.
pm_flags depends only on CONFIG_PM,
which is present for both CONFIG_APM and CONFIG_ACPI.

http://bugzilla.kernel.org/show_bug.cgi?id=9194

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

kernel/power/main.c

@@ -28,6 +28,9 @@ BLOCKING_NOTIFIER_HEAD(pm_chain_head);
 
 DEFINE_MUTEX(pm_mutex);
 
+unsigned int pm_flags;
+EXPORT_SYMBOL(pm_flags);
+
 #ifdef CONFIG_SUSPEND
 
 /* This is just an arbitrary number */