cgroup: use legacy_name for cgroup v1 disable info

cgroup v1 or v2 or both controller names can be passed as arguments to
the 'cgroup_no_v1' kernel parameter, though most of the controller's
names are the same for both cgroup versions. This can be confusing when
both versions are used interchangeably, i.e., passing cgroup_no_v1=io

$ sudo dmesg |grep cgroup
...
cgroup: Disabling io control group subsystem in v1 mounts
cgroup: Disabled controller 'blkio'

Make it consistent across the pr_info()'s, by using ss->legacy_name, as
the subsystem name, while printing the cgroup v1 controller disabling
information in cgroup_init().

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: kamalesh-babulal

kernel/cgroup/cgroup.c

@@ -6127,7 +6127,7 @@ int __init cgroup_init(void)
 
 		if (cgroup1_ssid_disabled(ssid))
 			pr_info("Disabling %s control group subsystem in v1 mounts\n",
-				ss->name);
+				ss->legacy_name);
 
 		cgrp_dfl_root.subsys_mask |= 1 << ss->id;