Icon: use size_hint_min instead of image_size to know the wanted size

This @fix fdo icons to load the correct image for the requested size.

Whitout this the small images (16x16) was never used, because once a big
(64x64 for example) image was loaded, that size was used as min.

See the Icon Standard test for a better explanation

legacy/elementary/src/lib/elm_icon.c

@@ -52,7 +52,7 @@ _icon_size_min_get(Evas_Object *icon)
 {
    int size;
 
-   elm_image_object_size_get(icon, &size, NULL);
+   evas_object_size_hint_min_get(icon, &size, NULL);
 
    return (size < 16) ? 16 : size;
 }