[PATCH] mm: make page migration dependent on swap and NUMA

The page migration code could function without NUMA but we currently have
no users for the non-NUMA case.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>