v2: update cgroups.txt instead of creating a new file

Cc: Li Zefan <redacted>
Cc: Tejun Heo <redacted>
Cc: Hugh Dickins <redacted>
Cc: Hillf Danton <redacted>
Cc: Lennart Poettering <redacted>
Signed-off-by: Aristeu Rozanski <redacted>

Acked-by: Li Zefan <redacted>

---
 Documentation/cgroups/cgroups.txt |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)