cgroup: unexport cgroup_rstat_updated

cgroup_rstat_updated is only used by core block code, no need to
export it.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

kernel/cgroup/rstat.c

@@ -64,7 +64,6 @@ void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
 
 	raw_spin_unlock_irqrestore(cpu_lock, flags);
 }
-EXPORT_SYMBOL_GPL(cgroup_rstat_updated);
 
 /**
  * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree