net: hns3: add support for querying advertised pause frame by ethtool ethx

This patch adds support for querying advertised pause frame by using
ethtool command(ethtool ethx).

Fixes: 496d03e9 ("net: hns3: Add Ethtool support to HNS3 driver")
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>