For that, use netdev_adjacent_get_private(list_head) on bond's lower
neighbour list members. Also, add a small macro - bond_slave_list(bond),
which returns the bond list via neighbour list.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>