net: hns3: add support for traffic class tuple support for flow director by ethtool

The hardware supports to parse and match the traffic class field
of IPv6 packet for flow director, uses the same tuple as ip tos.
So removes the limitation of configure 'tclass' by driver.

Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>