mlxsw: spectrum_ethtool: Add support for two new link modes

As part of a process for supporting a new system with RJ45 connectors,
100BaseT and 1000BaseT link modes need to be supported.

Add support for these two link modes by adding the two corresponding
bits in PTYS (Port Type and Speed) register.

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>