The arch-independent bootmem code now requires that arches initialize
their bootmem maps in reverse order (in particular, from high to low
addesses), otherwise alloc_bootmem_pages_low() won't work.  This change
makes the ia64 code do just that, so that machines without an IOMMU can
allocate their bounce buffers in low memory at early boot.  It also adds
a sanity check to the early init code to make sure that each node has a
local data area, because if they don't, many things will break later on
and may be hard to track down.