net: hns3: Add support for IFF_ALLMULTI flag

This patch adds support for IFF_ALLMULTI flag to HNS3 PF and VF
driver.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>