devlink: Add comment block for missing port attributes

Add comment block for physical, PF and VF port attributes.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>