Pull cgroup updates from Tejun Heo:
 "Two minor changes.

  One makes cgroup interface files ignore zero-sized writes rather than
  triggering -EINVAL on them. The other change is a cleanup which
  doesn't cause any behavior changes"

* 'for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Zero sized write should be no-op
  cgroup: remove redundant kernfs_activate in cgroup_setup_root()