bonding: remove bond_for_each_slave_continue_reverse()

We only use it in rollback scenarios and can easily use the standart
bond_for_each_dev() instead.

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>