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/cfq-iosched.c b/block/cfq-iosched.c
index 38277e3..baa8459 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1944,7 +1944,7 @@
 }
 #endif	/* CONFIG_DEBUG_BLK_CGROUP */
 
-static struct cftype cfq_blkcg_files[] = {
+static struct cftype cfq_blkcg_legacy_files[] = {
 	/* on root, weight is mapped to leaf_weight */
 	{
 		.name = "weight_device",
@@ -4654,7 +4654,7 @@
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
 static struct blkcg_policy blkcg_policy_cfq = {
-	.cftypes		= cfq_blkcg_files,
+	.legacy_cftypes		= cfq_blkcg_legacy_files,
 
 	.cpd_alloc_fn		= cfq_cpd_alloc,
 	.cpd_init_fn		= cfq_cpd_init,