net: hns3: Fix to support autoneg only for port attached with phy

This patch adds a check to support autoneg(ethtool -A) only when PHY
is attached with the port.

Fixes: e2cb1dec ("net: hns3: Add HNS3 VF HCL(Hardware Compatibility
Layer) Support")
Signed-off-by: Fuyun Liang <liangfuyun1@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>