bonding: add option lp_interval for loading module

The bond driver could set the lp_interval when loading module.

Suggested-by: Scott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>