net: hns3: Cleanup for non-static function in hns3 driver

This patch fixes the following warning from sparse:
warning: symbol 'hns3_set_multicast_list' was not declared.
Should it be static.

hns3_set_multicast_list turns out to be not used, so delete it.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>