ethtool: Add support for 800Gbps link modes

Add support for 800Gbps speed, link modes of 100Gbps per lane.
As mentioned in slide 21 in IEEE documentation [1], all adopted 802.3df
copper and optical PMDs baselines using 100G/lane will be supported.

Add the relevant PMDs which are mentioned in slide 5 in IEEE
documentation [1] and were approved on 10-2022 [2]:
BP - KR8
Cu Cable - CR8
MMF 50m - VR8
MMF 100m - SR8
SMF 500m - DR8
SMF 2km - DR8-2

[1]: https://www.ieee802.org/3/df/public/22_10/22_1004/shrikhande_3df_01a_221004.pdf
[2]: https://ieee802.org/3/df/KeyMotions_3df_221005.pdf

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>