nfp: update devlink device info output

Newer NIC will introduce a new part number, now add it
into devlink device info.

This patch also updates the information of "board.id" in
nfp.rst to match the devlink-info.rst.

Signed-off-by: Fei Qin <fei.qin@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>