Re-work the m68knommu specific idle code according to suggestions
from Nick Piggin <nickpiggin@yahoo.com.au>.

A couple of rules that we need to follow:

1. Preempt should now disabled over idle routines. Should only be enabled
to call schedule() then disabled again.

3. When cpu_idle finds (need_resched() == 'true'), it should call schedule().
It should not call schedule() otherwise.

Also fix interrupt locking around the need_resched() and cpu stop state
so that there is no race condition.
Signed-off-by: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>