sched: Fix a trivial syntax misuse

Use if statement instead of while loop.

Signed-off-by: Shigeru Yoshida <shigeru.yoshida@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <trivial@kernel.org>
Link: http://lkml.kernel.org/r/20131123.183801.769652906919404319.shigeru.yoshida@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -3654,7 +3654,7 @@ bool __sched yield_to(struct task_struct *p, bool preempt)
 	}
 
 	double_rq_lock(rq, p_rq);
-	while (task_rq(p) != p_rq) {
+	if (task_rq(p) != p_rq) {
 		double_rq_unlock(rq, p_rq);
 		goto again;
 	}