usb: sandbox: Add DM_USB_GADGET support

Remove local usb_gadget_register_driver()/usb_gadget_unregister_driver()
implementation which is implemented in udc-core.c instead if DM_USB_GADGET
is enabled. Add no-op dm_usb_gadget_handle_interrupts() implementation.

Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Marek Vasut <marex@denx.de>

drivers/usb/host/usb-sandbox.c

@@ -124,6 +124,12 @@ static int sandbox_submit_int(struct udevice *bus, struct usb_device *udev,
 	return ret;
 }
 
+#if CONFIG_IS_ENABLED(DM_USB_GADGET)
+int dm_usb_gadget_handle_interrupts(struct udevice *dev)
+{
+	return 0;
+}
+#else
 int usb_gadget_handle_interrupts(int index)
 {
 	return 0;
@@ -144,6 +150,7 @@ int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
 
 	return 0;
 }
+#endif
 
 static int sandbox_alloc_device(struct udevice *dev, struct usb_device *udev)
 {