Work around Dell E520 BIOS reboot bug

Force Dell E520 to use the BIOS to shutdown/reboot.

I have at least one report that this patch fixes shutdown/reboot
problems on the Dell E520 platform.

(Andi says: People can always set the boot option.  It hardly seems like a
critical issue needing a backport.)

Signed-off-by: Tim Gardner <tim.gardner@ubuntu.com>
Acked-by: Andi Kleen <ak@suse.de>
Acked-by: Matt Domsch <Matt_Domsch@dell.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>