trivial: fix where cgroup documentation is not correctly referred to

cgroup documentation was moved to Documentation/cgroups/. There are some
places that still refer to Documentation/controllers/,
Documentation/cgroups.txt and Documentation/cpusets.txt. Fix those.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/vm/page_migration b/Documentation/vm/page_migration
index d5fdfd3..6513fe2 100644
--- a/Documentation/vm/page_migration
+++ b/Documentation/vm/page_migration
@@ -37,7 +37,8 @@
 
 Larger installations usually partition the system using cpusets into
 sections of nodes. Paul Jackson has equipped cpusets with the ability to
-move pages when a task is moved to another cpuset (See ../cpusets.txt).
+move pages when a task is moved to another cpuset (See
+Documentation/cgroups/cpusets.txt).
 Cpusets allows the automation of process locality. If a task is moved to
 a new cpuset then also all its pages are moved with it so that the
 performance of the process does not sink dramatically. Also the pages