Hibernation: Make sure that ACPI is enabled in acpi_hibernation_finish

If the BIOS does not enable ACPI and the "acpi=off" command line parameter
is passed to the boot kernel, ACPI may be disabled when the (restored)
image kernel attempts to execute acpi_hibernation_finish().  To prevent
this from happening we can call acpi_enable() from
acpi_hibernation_finish() (if ACPI is already enabled, this will have no
effect).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>