selftests/bpf: Add test for bpf_get_func_ip in kprobe+offset probe

Adding test for bpf_get_func_ip in kprobe+ofset probe.
Because of the offset value it's arch specific, enabling
the new test only for x86_64 architecture.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-9-jolsa@kernel.org