Hello All,
  The following patch reserves the nodes_add data for use later.  It
retains the bulk of the hotadd_precent defense that is built into the
SRAT code. It is a little subtle but it gets the job done.  

  The code saves off the hot-add area ranges without extending the end
of memory.  It then creates arch_find_node which will be use in the next
patch.  

 arch_find_node is passed a memory range and it looks for a nodes_add
area it fits into.   If no area is found it returns 0.

 With this and the other 3 patches I can do SPARSEMEM x86_64 hot-add on
my hardware. (the first 2 patches are one I consider real the other 2
are more to point out issues)

 It is built against 2.6.17-mm1 x86_64 and the current memory_hotplug
work but should apply on any current srat.c

Signed-off-by:  Keith Mannthey <kmannth@us.ibm.com>