nfp: bpf: reject program on instructions unknown to the JIT compiler

If an eBPF instruction is unknown to the driver JIT compiler, we can
reject the program at verification time.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>