IB/mlx5: Adjust mlx5 rate mapping to support 800Gb

Adjust mlx5 function which maps the speed rate from IB spec values
to internal driver values to be able to handle speeds up to 800Gb.

Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Mark Zhang <markzhang@nvidia.com>
Link: https://lore.kernel.org/r/301c803d8486b0df8aefad3fb3cc10dc58671985.1695204156.git.leon@kernel.org


Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>