[PATCH] x86_64: Eliminate register_die_notifier symbol exported

register_die_notifier is exported twice, once in traps.c and once in
x8664_ksyms.c.  This results in a warning on build.

Signed-off-by: Kevin Winchester <kwin@ns.sympatico.ca>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>