RDMA: Fix link active_speed size

According to the IB spec active_speed size should be u16 and not u8 as
before. Changing it to allow further extensions in offered speeds.

Link: https://lore.kernel.org/r/20200917090223.1018224-4-leon@kernel.org


Signed-off-by: Aharon Landau <aharonl@mellanox.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>