move irqhandler to application

tud_isr() must be called by application to forward the irqhandle to the
stack

hw/bsp/feather_nrf52840_express/feather_nrf52840_express.c

@@ -92,6 +92,7 @@ void board_init(void)
 
   nrfx_uarte_init(&_uart_id, &uart_cfg, NULL); //uart_handler);
 
+  //------------- USB -------------//
 #if TUSB_OPT_DEVICE_ENABLED
   // Priorities 0, 1, 4 (nRF52) are reserved for SoftDevice
   // 2 is highest for application