You can use my functions :
first change your code
to
and second add between your tags
$( "#target" ).toggle(function() {
selectAll($( "#divRatings" ))
}, function() {
selectClear($( "#divRatings" ))
});
function selectAll(element){//Select All Function
element.prop('selected', true);
element.selectpicker('refresh');
}
function selectClear(element){//Clear All Function
element.prop('selected', false);
element.selectpicker('refresh');
}