net: hns3: add ethtool related offload command

This patch adds offload command related to "ethtool -K".

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>