fs/proc: do_task_stat: use __for_each_thread()

fs/proc: do_task_stat: use __for_each_thread()

commit 7904e53ed5a20fc678c01d5d1b07ec486425bb6a upstream.

do/while_each_thread should be avoided when possible.

Link: https://lkml.kernel.org/r/20230909164501.GA11581@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 7601df8031fd ("fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats")
Cc: stable@vger.kernel.org
[ mheyne: adjusted context ]
Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>