dm stats: fix a leaked s->histogram_boundaries array

Fixes: dfcfac3e4cd9 ("dm stats: collect and report histogram of IO latencies")
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 38b05f2..0250e7e 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -175,6 +175,7 @@
 	int cpu;
 	struct dm_stat *s = container_of(head, struct dm_stat, rcu_head);
 
+	kfree(s->histogram_boundaries);
 	kfree(s->program_id);
 	kfree(s->aux_data);
 	for_each_possible_cpu(cpu) {