net: hns3: add support for set_pauseparam

This patch adds set_pauseparam support for ethtool cmd.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Fuyun Liang <liangfuyun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>