<?php


$items =  [
    ['usu_codigo' => 1, /** resto do array **/],
    ['usu_codigo'   => 2, /** resto do array **/],
    ['usu_codigo'   => 3, /** resto do array **/],
];


usort($items, function ($a, $b)  {
	
	return $b['usu_codigo'] - $a['usu_codigo'];
});


print_r($items);