From: Dave Hansen <haveblue@us.ibm.com>

As described in this bug: http://bugme.osdl.org/show_bug.cgi?id=653 , if
you enable Summit support and NUMA Discontigmem support but boot on a
non-Summit box, the kernel will fail to boot.  The problem is that the
Summit code can not correctly get the NUMA memory configuration of a
flat box.  The code to do that is in get_memcfg_numa_flat(), but it
never gets called.

This patch implements a fallback to the generic NUMA code in
get_memcfg_numa_flat() if the Summit detection fails.  The patch also
adds the necessary bits to the Summit code so that it *knows* when it
fails.