bpf, nfp: implement jiting of BPF_J{LT,LE}

This work implements jiting of BPF_J{LT,LE} instructions with
BPF_X/BPF_K variants for the nfp eBPF JIT. The two BPF_J{SLT,SLE}
instructions have not been added yet given BPF_J{SGT,SGE} are
not supported yet either.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>