selftests/bpf: fix perf_event link info name_len assertion

Fix `name_len` field assertions in `bpf_link_info.perf_event` for
kprobe/uprobe/tracepoint to validate correct name size instead of 0.

Fixes: 23cf7aa5 ("selftests/bpf: Add selftest for fill_link_info")
Signed-off-by: Tyrone Wu <wudevelops@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20241008164312.46269-2-wudevelops@gmail.com


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