nfp: add devlink param infrastructure

Register devlink parameters for driver use. Subsequent patches will add
support for specific parameters.

In order to support devlink parameters, the management firmware needs to
be able to lookup and set hwinfo keys.

Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>