blkcg: mark existing cftypes as legacy

blkcg is about to grow interface for the unified hierarchy.  Add
legacy to existing cftypes.

* blkcg_policy->cftypes -> blkcg_policy->legacy_cftypes
* blk-cgroup.c:blkcg_files -> blkcg_legacy_files
* cfq-iosched.c:cfq_blkcg_files -> cfq_blkcg_legacy_files
* blk-throttle.c:throtl_files -> throtl_legacy_files

Pure renames.  No functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index bd3e4b2..8b4f6b8 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1217,7 +1217,7 @@
 	return tg_set_conf(of, buf, nbytes, off, false);
 }
 
-static struct cftype throtl_files[] = {
+static struct cftype throtl_legacy_files[] = {
 	{
 		.name = "throttle.read_bps_device",
 		.private = offsetof(struct throtl_grp, bps[READ]),
@@ -1263,7 +1263,7 @@
 }
 
 static struct blkcg_policy blkcg_policy_throtl = {
-	.cftypes		= throtl_files,
+	.legacy_cftypes		= throtl_legacy_files,
 
 	.pd_alloc_fn		= throtl_pd_alloc,
 	.pd_init_fn		= throtl_pd_init,