nfp: debug dump ethtool ops

- Skeleton code to perform a binary debug dump via ethtoolops
  "set_dump", "get_dump_flags" and "get_dump_data", i.e. the ethtool
  -W/w mechanism.
- Skeleton functions for debugdump operations provided.
- An integer "dump level" can be specified, this is stored between
  ethtool invocations. Dump level 0 is still the "arm.diag" resource for
  backward compatibility. Other dump levels each define a set of state
  information to include in the dump, driven by a spec from FW.

Signed-off-by: Carl Heymann <carl.heymann@netronome.com>
Reviewed-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>