IB/mlx5: Use rdma_for_each_port for port iteration

IB/mlx5: Use rdma_for_each_port for port iteration

Instead of open coding the loop for port iteration, use rdma_for_each_port
macro provided by core.

To use such macro, early initialization of phys_port_cnt is needed.
Hence, initialize such constant early enough in the init stage.

Whichever functions are called with port using rdma_for_each_port(),
convert their port type from u8 to unsigned int to match the core API.

Link: https://lore.kernel.org/r/20210203130133.4057329-6-leon@kernel.org
Signed-off-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>