doc: rcu: Encourage use of rcu_barrier in checklist

The checklist suggests rcu_barrier_bh() for RCU-bh and similarly for
sched, however these APIs are now implemented as rcu_barrier() itself due
to the RCU consolidation. This commit therefore corrects checklist.txt
to encourage use of the underlying rcu_barrier() API.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

Documentation/RCU/checklist.txt

@@ -442,8 +442,8 @@ over a rather long period of time, but improvements are always welcome!
 	You instead need to use one of the barrier functions:
 
 	o	call_rcu() -> rcu_barrier()
-	o	call_rcu_bh() -> rcu_barrier_bh()
-	o	call_rcu_sched() -> rcu_barrier_sched()
+	o	call_rcu_bh() -> rcu_barrier()
+	o	call_rcu_sched() -> rcu_barrier()
 	o	call_srcu() -> srcu_barrier()
 
 	However, these barrier functions are absolutely -not- guaranteed