docs: cgroup-v1: add it to the admin-guide book

Those files belong to the admin guide, so add them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

kernel/cgroup/cpuset.c

@@ -729,7 +729,7 @@ static inline int nr_cpusets(void)
  * load balancing domains (sched domains) as specified by that partial
  * partition.
  *
- * See "What is sched_load_balance" in Documentation/cgroup-v1/cpusets.rst
+ * See "What is sched_load_balance" in Documentation/admin-guide/cgroup-v1/cpusets.rst
  * for a background explanation of this.
  *
  * Does not return errors, on the theory that the callers of this