[PATCH] x86_64: add x86-64 support for memory hot-add

Add x86-64 specific memory hot-add functions, Kconfig options,
and runtime kernel page table update functions to make
hot-add usable on x86-64 machines.  Also, fixup the nefarious
conditional locking and exports pointed out by Andi.

Tested on Intel and IBM x86-64 memory hot-add capable systems.

Signed-off-by: Matt Tolentino <matthew.e.tolentino@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>