Revert "PM: ACPI: reboot: Use S5 for reboot"

This reverts commit d60cd063

.

This patch causes a panic when rebooting my Dell Poweredge r440.  I do
not have the full panic log as it's lost at that stage of the reboot and
I do not have a serial console.  Reverting this patch makes my system
able to reboot again.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>