RDMA/mlx5: Move to single device multiport ports in switchdev mode

Move from IB device (representor) per virtual function to single IB device
with port per virtual function (port 1 represents the uplink). As number
of ports is a static property of an IB device, declare the IB device with
as many port as the possible according to the PCI bus.

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