Merge branch 'bpf-enable-some-functions-in-cgroup-programs'

Matteo Croce says:

====================
bpf: enable some functions in cgroup programs

From: Matteo Croce <teknoraver@meta.com>

Enable some BPF kfuncs and the helper bpf_current_task_under_cgroup()
for program types BPF_CGROUP_*.
These will be used by systemd-networkd:
https://github.com/systemd/systemd/pull/32212

v5->v6:
Called register_btf_kfunc_id_set() only once
Fixed build error with !CONFIG_CGROUPS

v4->v5:
Same code, but v4 had an old cover letter

v3->v4:
Reset all the acked-by tags because the code changed a bit.

Signed-off-by: Matteo Croce <teknoraver@meta.com>
====================

Link: https://lore.kernel.org/r/20240819162805.78235-1-technoboy85@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>