The current MEMORY_HOTPLUG code expects that the ACPI layer (for the
Intel space) will pass along the _PXM data (this is node locality data).
This is an optional field for the acpi namespace and one which Linux
should not require for hot-add memory. 

  This patch creates uses the arch_find_node function and wedges it into
the generic add_memory function.  When the acpi can't resolve the _PXM
data (as in my hardware event) it returns -1.  I build a check into
add_memory that looks for invalid data passes id < 0 and calls
arch_find_node.  
  
  I intend to implement an arch_find_node for i386 in the near
future.     


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