On architectures that implement sparsemem but not discontigmem we want to
be able to hide the flatmem option in some cases.  On ppc64 for example,
when we select NUMA we must not select flatmem.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>