nfp: flower: app should use struct nfp_repr

Ensure priv netdev data in flower app is cast to nfp_repr and not nfp_net
as in other apps.

Fixes: 363fc53b ("nfp: flower: Convert ndo_setup_tc offloads to block callbacks")
Signed-off-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>