sched/core: Remove rq_relock()

After the removal of migrate_tasks(), there is no user of
rq_relock() left, so remove it.
Signed-off-by: Peng Wang <rocking@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/449948fdf9be4764b3929c52572917dd25eef758.1634611953.git.rocking@linux.alibaba.com

kernel/sched/sched.h

@@ -1615,14 +1615,6 @@ rq_lock(struct rq *rq, struct rq_flags *rf)
 	rq_pin_lock(rq, rf);
 }
 
-static inline void
-rq_relock(struct rq *rq, struct rq_flags *rf)
-	__acquires(rq->lock)
-{
-	raw_spin_rq_lock(rq);
-	rq_repin_lock(rq, rf);
-}
-
 static inline void
 rq_unlock_irqrestore(struct rq *rq, struct rq_flags *rf)
 	__releases(rq->lock)