From: Olof Johansson <olof@austin.ibm.com>

As discussed on the ppc64 list yesterday and today:

On some ppc64 systems, Open Firmware will give memory device nodes that are
only 16MB in size, instead of the 256MB that our NUMA code currently
expects (see MEMORY_INCREMENT in mmzone.h).

Just changing the defines from 256MB to 16MB makes the table blow up from
32KB to 512KB, so this patch also makes it dynamically allocated based on
actual memory size.  Since all this is done before (well, during) bootmem
init so we need to use lmb_alloc().

Finally, there's no need to use a full int for node ID. Current max is 16
nodes, so a signed char still leaves plenty of room to grow.