selftests/bpf: skip recursive functions for kprobe_multi

Some functions is recursive for the kprobe_multi and impact the benchmark
results. So just skip them.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20250904021011.14069-3-dongml2@chinatelecom.cn


Signed-off-by: Alexei Starovoitov <ast@kernel.org>