acpi: fix potential call to a freed memory section.

Strip __cpuinit[data] from Node <-> PXM routines and supporting data
structures.  Also make pxm_to_node_map and node_to_pxm_map local to the
numa acpi module.

This fixes a bug triggered by the following conditions:
- boot on a machine with a SLIT table defined
- kernel is configured w/ CONFIG_HOTPLUG_CPU=n
- cat /sys/devices/system/node/node*/distance
This will cause an oops by calling into a freed memory section.

In particular, on x86_64, __node_distance calls node_to_pxm().

Signed-off-by: Aaron Durbin <adurbin@google.com>
Cc: Len Brown <lenb@kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>