devlink: Refactor physical port attributes

To support additional devlink port flavours and to support few common
and few different port attributes, move physical port attributes to a
different structure.

Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>