nfp: bpf: require ETH table

Upcoming changes will require all netdevs supporting TC offloads
to have a full struct nfp_port.  Require those for BPF offload.
The operation without management FW reporting information about
Ethernet ports is something we only support for very old and very
basic NIC firmwares anyway.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Tested-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>