blk-throttle: Free up policy node associated with deleted rule

If a rule is being deleted, free up associated policy node. Otherwise
that memory is leaked.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d61ec56..6155367 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1075,6 +1075,7 @@
 
 	if (blkio_delete_rule_command(newpn)) {
 		blkio_policy_delete_node(pn);
+		kfree(pn);
 		spin_unlock_irq(&blkcg->lock);
 		goto update_io_group;
 	}