revert "sched: fix fair sleepers"

revert "sched: fix fair sleepers" (e22ecef1),
because it is causing audio skipping, see:

   http://bugzilla.kernel.org/show_bug.cgi?id=10428



the patch is correct and the real cause of the skipping is not
understood (tracing makes it go away), but time has run out so we'll
revert it and re-try in 2.6.26.

Signed-off-by: Ingo Molnar <mingo@elte.hu>