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 <[e-mail]>
Reported-by: Ingo Molnar <[e-mail]>
Signed-off-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Peter Zijlstra <[e-mail]>
LKML-Reference: <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/sched.h

···
  * cond_resched_softirq() will enable bhs before scheduling.
  */
 extern int _cond_resched(void);
-#ifdef CONFIG_PREEMPT_BKL
-static inline int cond_resched(void)
-{
-	return 0;
-}
-#else
+
 static inline int cond_resched(void)
 {
 	return _cond_resched();
 }
-#endif
+
 extern int cond_resched_lock(spinlock_t * lock);
 extern int cond_resched_softirq(void);
 static inline int cond_resched_bkl(void)