selftests/bpf: fix test_attach_probe map definition

ef99b02b ("libbpf: capture value in BTF type info for BTF-defined map
defs") changed BTF-defined maps syntax, while independently merged
1e8611bb ("selftests/bpf: add kprobe/uprobe selftests") added new
test using outdated syntax of maps. This patch fixes this test after
corresponding patch sets were merged.

Fixes: ef99b02b ("libbpf: capture value in BTF type info for BTF-defined map defs")
Fixes: 1e8611bb ("selftests/bpf: add kprobe/uprobe selftests")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>