nfp: add extended error messages

Allow NSP to set option code even when error is reported.  This provides
a way for NSP to give user more precise information about why command
failed.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>