bonding: remove the redundant judgements for bond_set_mac_address()

The dev_set_mac_address() will check the dev->netdev_ops->ndo_set_mac_address,
so no need to check it in bond_set_mac_address().

Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>