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>
diff --git a/block/Kconfig b/block/Kconfig
index b16b3e0..8b5f8e5 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -89,7 +89,7 @@
 	one needs to mount and use blkio cgroup controller for creating
 	cgroups and specifying per device IO rate policies.
 
-	See Documentation/cgroup-v1/blkio-controller.rst for more information.
+	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
 
 config BLK_DEV_THROTTLING_LOW
 	bool "Block throttling .low limit interface support (EXPERIMENTAL)"