sched: replace MAX_NUMNODES with nr_node_ids in kernel/sched.c

  * Replace usages of MAX_NUMNODES with nr_node_ids in kernel/sched.c,
    where appropriate.  This saves some allocated space as well as many
    wasted cycles going through node entries that are non-existent.

For inclusion into sched-devel/latest tree.

Based on:
	git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
    +   sched-devel/latest  .../mingo/linux-2.6-sched-devel.git

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>