sched/wait: Change the wait_exclusive control flow

Purely a preparatory patch; it changes the control flow to match what
will soon be generated by generic code so that that patch can be a
unity transform.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131002092528.107994763@infradead.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>