At the moment, we initialise physnode_map from the various BIOS tables,
which can create problems, as holes inside an node return 1 for pfn_valid,
and yet pfn_to_nid is not correct for them.  I'd hacked around this in my
tree by defaulting the mapping to 0, not -1, but that's not the correct fix
...  this is.

I consolidated all the code back into 1 place, and use node_start_pfn[] and
node_end_pfn[] to walk over it instead - that means it matches up perfectly
with lmem_map's as we're using the same data.  It also cleans up a lot of
the code.

Tested on both NUMA-Q and x440 ...  and it only affects i386 NUMA boxen.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>