tools/bpf: fix test_btf for typedef func_proto case

Fixed one test_btf raw test such that typedef func_proto
is permitted now.

Fixes: 78a2540e

 ("tools/bpf: Add tests for BTF_KIND_FUNC_PROTO and BTF_KIND_FUNC")
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>