RDMA/mlx5: Move SMI caps logic

We store the SMI information in the core device's struct, make sure we set
that information only once (and not per port), while here make the for
loop based on the actual size of the array.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>