bpf: add test cases for new BPF_J{LT, LE, SLT, SLE} instructions

Add test cases to the verifier selftest suite in order to verify that
i) direct packet access, and ii) dynamic map value access is working
with the changes related to the new instructions.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>