audit: annotate the lockless read of the audit control lock owner

audit_ctl_owner_current() reads the lock owner without taking the lock
and KCSAN complains about it. Only the current task can store itself as
owner, so the check can't give a wrong answer. Mark the accesses with
READ_ONCE() and WRITE_ONCE().

Reported-by: syzbot+39b8fea0641107a1ccee@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=39b8fea0641107a1ccee
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Babanpreet Singh <bbnpreetsingh@gmail.com>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Tested-by: Bradley Morgan <brads@mainlining.org> # Power10
Signed-off-by: Paul Moore <paul@paul-moore.com>