fix usb test some bug

usrc/service/app_core.cpp

@@ -47,6 +47,7 @@ void umain() { AppCore::ins()->initialize(); }
 }
 extern "C" {
 extern void MX_USB_HOST_Init(void);
+extern void MX_FATFS_Init();
 }
 void AppCore::test() {
   osDelay(1000);
@@ -206,6 +207,7 @@ void AppCore::test() {
 
   ZGPIO USB_PWR;
   USB_PWR.initAsOutput(PA15, kxs_gpio_nopull, false, true);
+  MX_FATFS_Init();
   MX_USB_HOST_Init();
   while (true) {
     osDelay(1000);