net: hns: add multicast tcam table clear

There is no clear operation before add a new multicast tcam table,
so the tcam table will be overflow when add more entries.

Reported-by: Daode Huang <huangdaode@hisilicon.com>
Signed-off-by: Kejian Yan <yankejian@huawei.com>
Reviewed-by: Yisen Zhuang <yisen.zhuang@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>