Removes the un/set_nmi_callback and reserve/release_lapic_nmi functions as
they are no longer needed.  The various subsystems are modified to register
with the die_notifier instead.

Also includes compile fixes by Andrew Morton.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NAndi Kleen <ak@suse.de>