selftests/bpf: Add test for bpf_get_func_ip helper

Adding test for bpf_get_func_ip helper for fentry, fexit,
kprobe, kretprobe and fmod_ret programs.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-6-jolsa@kernel.org