net/mlx5: Enable 4 ports multiport E-switch

enable_mpesw() assumed only 2 ports are available, fix this by removing
that assumption and looping through the existing lag ports to enable multi-port
E-switch for cards with more than 2 ports.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>