[PATCH] ppc64 memory model depends on NUMA

Currently when we first select memory model (FLAT, DISCONTIG, SPARSE) then
select whether the machine is NUMA.  However NUMA systems may not be FLAT.
This constraint it not honoured and we may configure a NUMA/FLAT system.

Reorder the configuration such that we choose NUMA first which allows us to
only list the memory models which are valid.  We now default NUMA for known
NUMA systems.  Note that this new order also matches that used in x86.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>