Revert "dm: usb: Use device_unbind_children to clean up usb devs on stop"

This reverts commit 6cda369509e0d3fa5f9e33c9d71589c4523799fa.

We want to avoid having the USB stack rely on unbind.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/host/usb-uclass.c b/drivers/usb/host/usb-uclass.c
index 838d05a..89611f1 100644
--- a/drivers/usb/host/usb-uclass.c
+++ b/drivers/usb/host/usb-uclass.c
@@ -158,9 +158,6 @@
 		ret = device_remove(bus);
 		if (ret && !err)
 			err = ret;
-		ret = device_unbind_children(bus);
-		if (ret && !err)
-			err = ret;
 	}
 
 #ifdef CONFIG_SANDBOX