Merge branch 'bpf-add-support-for-cgroup1-bpf-part'

Yafang Shao says:

====================
bpf: Add support for cgroup1, BPF part

This is the BPF part of the series "bpf, cgroup: Add BPF support for
cgroup1 hierarchy" with adjustment in the last two patches compared
to the previous one.

v3->v4:
  - use subsys_name instead of cgrp_name in get_cgroup_hierarchy_id()
    (Tejun)
  - use local bpf_link instead of modifying the skeleton in the
    selftests
v3: https://lwn.net/Articles/949264/
====================

Link: https://lore.kernel.org/r/20231111090034.4248-1-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>