libbpf: Fix signedness bug in btf_dump_array_data()

The btf__resolve_size() function returns negative error codes so
"elem_size" must be signed for the error handling to work.

Fixes: 920d16af ("libbpf: BTF dumper support for typed data")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220208071552.GB10495@kili

tools/lib/bpf/btf_dump.c

@@ -1861,14 +1861,15 @@ static int btf_dump_array_data(struct btf_dump *d,
 {
 	const struct btf_array *array = btf_array(t);
 	const struct btf_type *elem_type;
-	__u32 i, elem_size = 0, elem_type_id;
+	__u32 i, elem_type_id;
+	__s64 elem_size;
 	bool is_array_member;
 
 	elem_type_id = array->type;
 	elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
 	elem_size = btf__resolve_size(d->btf, elem_type_id);
 	if (elem_size <= 0) {
-		pr_warn("unexpected elem size %d for array type [%u]\n", elem_size, id);
+		pr_warn("unexpected elem size %lld for array type [%u]\n", elem_size, id);
 		return -EINVAL;
 	}