rcu: Consolidate RCU-bh update-side function definitions

This commit saves a few lines by consolidating the RCU-bh function
definitions at the end of include/linux/rcupdate.h.  This consolidation
also makes it easier to remove them all when the time comes.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -3252,15 +3252,6 @@ static void _rcu_barrier(void)
 	mutex_unlock(&rcu_state.barrier_mutex);
 }
 
-/**
- * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
- */
-void rcu_barrier_bh(void)
-{
-	_rcu_barrier();
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-
 /**
  * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
  *