Revert "x86: default to reboot via ACPI"

This reverts commit c7ffa6c26277b403920e2255d10df849bd613380.

the assumptio of this change was that this would not break
any existing machine. Andrey Borzenkov reported troubles with
the ACPI reboot method: the system would hang on reboot, necessiating
a power cycle. Probably more systems are affected as well.

Also, there are patches queued up for v2.6.29 to disable virtualization
on emergency_restart() - which was the original motivation of
this change.

Reported-by: Andrey Borzenkov <arvidjaar@mail.ru>
Bisected-by: Andrey Borzenkov <arvidjaar@mail.ru>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/reboot.c

@@ -29,11 +29,7 @@ EXPORT_SYMBOL(pm_power_off);
 
 static const struct desc_ptr no_idt = {};
 static int reboot_mode;
-/*
- * Keyboard reset and triple fault may result in INIT, not RESET, which
- * doesn't work when we're in vmx root mode.  Try ACPI first.
- */
-enum reboot_type reboot_type = BOOT_ACPI;
+enum reboot_type reboot_type = BOOT_KBD;
 int reboot_force;
 
 #if defined(CONFIG_X86_32) && defined(CONFIG_SMP)