dm: core: Adjust dump-sorting to get stats only when needed

If we are not sorting the tree we don't need to get the stats. Adjust the
code to avoid the wasted time.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/dump.c

@@ -90,9 +90,8 @@ static void dm_dump_tree_single(struct udevice *dev, bool sort)
 	int dev_count, uclasses;
 	struct udevice **devs = NULL;
 
-	dm_get_stats(&dev_count, &uclasses);
-
 	if (sort) {
+		dm_get_stats(&dev_count, &uclasses);
 		devs = calloc(dev_count, sizeof(struct udevice *));
 		if (!devs) {
 			printf("(out of memory)\n");