libbpf: fix max() type mismatch for 32bit

It fixes build error for 32bit caused by type mismatch
size_t/unsigned long.

Fixes: bf829271 ("libbpf: refactor map initialization")
Acked-by: NSong Liu <songliubraving@fb.com>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Signed-off-by: NIvan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/libbpf.c

@@ -778,7 +778,7 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
 	if (obj->nr_maps < obj->maps_cap)
 		return &obj->maps[obj->nr_maps++];
 
-	new_cap = max(4ul, obj->maps_cap * 3 / 2);
+	new_cap = max((size_t)4, obj->maps_cap * 3 / 2);
 	new_maps = realloc(obj->maps, new_cap * sizeof(*obj->maps));
 	if (!new_maps) {
 		pr_warning("alloc maps for object failed\n");