IB/mlx4: Fix port query for 56Gb Ethernet links

Report the correct speed in the port attributes when using a 56Gbps
ethernet link.  Without this change the field is incorrectly set to 10.

Fixes: a9c766bb ('IB/mlx4: Fix info returned when querying IBoE ports')
Fixes: 2e96691c ('IB: Use central enum for speed instead of hard-coded values')
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>