net: hns3: disable auto-negotiation off with 1000M setting in ethtool

The 802.3 specification does not specify the behavior of
auto-negotiation off with 1000M in PHY. Therefore, some PHY
compatibility issues occur. This patch forbids the setting of
this unreasonable mode by ethtool in driver.

Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>