Merge branch 'bpf-task_group_seq_get_next-misc-cleanups'

Oleg Nesterov says:

====================
bpf: task_group_seq_get_next: misc cleanups

Yonghong,

I am resending 1-5 of 6 as you suggested with your acks included.

The next (final) patch will change this code to use __next_thread when

	https://lore.kernel.org/all/20230824143142.GA31222@redhat.com/

is merged.

Oleg.
====================

Link: https://lore.kernel.org/r/20230905154612.GA24872@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>