sched: Remove the CONFIG_PREEMPT_BKL case definition of cond_resched()

CONFIG_PREEMPT_BKL doesn't exist anymore. So remove this
config-on case definition of cond_resched().

Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1247725694-6082-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>