IB/mlx4: Fix IBoE reported link rate

The link rate is the product of the link speed in the link width. For
Etherent ports the rate is 10G, so we use 1 for the width and 4 for
speed to get the correct rate.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>