Now that all RCU flavors have been consolidated, rcu_barrier_sched()
is but a synonym for rcu_barrier().  This commit therefore replaces
the former with the latter.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <linux-mm@kvack.org>