Added warning when re-booting and XS3 part

lib_xua/src/core/support/reboot.xc

@@ -38,6 +38,8 @@ void device_reboot(void)
     /* Disconnect from bus */
     unsigned data[] = {4};
     write_periph_32(usb_tile, XS2_SU_PERIPH_USB_ID, XS1_GLX_PER_UIFM_FUNC_CONTROL_NUM, 1, data);
+#elif defined(__XS3A__)
+    #warning Assuming that tile reset also resets USB in XS3 architectures
 #endif
 
     tileArrayLength = sizeof(tile)/sizeof(tileref);