Add support for configuring port split with devlink.  Add devlink
callbacks to validate requested config and call NSP helpers.
Getting the right nfp_port structure can be done with simple iteration.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NSimon Horman <simon.horman@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>