Only keep bond_option_active_slave_get_rcu() helper.

bond_fill_info() uses a new bond_option_active_slave_get_ifindex()
helper.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Acked-by: NVeaceslav Falico <vfalico@gmail.com>
Reviewed-by: NNikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>