rcu: Remove unused rdp local from synchronize_rcu_expedited()

Because rdp is initialized but never used in synchronize_rcu_expedited(),
this commit removes it.

Signed-off-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index e0c928d..8e53971 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -793,7 +793,6 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
  */
 void synchronize_rcu_expedited(void)
 {
-	struct rcu_data *rdp;
 	struct rcu_exp_work rew;
 	struct rcu_node *rnp;
 	unsigned long s;
@@ -830,7 +829,6 @@ void synchronize_rcu_expedited(void)
 	}
 
 	/* Wait for expedited grace period to complete. */
-	rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
 	rnp = rcu_get_root();
 	wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
 		   sync_exp_work_done(s));