Port over a i386 kludge from rusty to x86-64

I don't think it is a full solution, but the upcomming smp bootup rewrite
will solve it.

This fixes BUGs at bootup on bigger x86-64 systems.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>