fix esp32 msc example

examples/host/cdc_msc_hid_freertos/src/msc_app.c

@@ -25,10 +25,12 @@
 
 #include "tusb.h"
 
-#if CFG_TUH_MSC
-
 static scsi_inquiry_resp_t inquiry_resp;
 
+void msc_app_init(void) {
+  // nothing to do
+}
+
 bool inquiry_complete_cb(uint8_t dev_addr, tuh_msc_complete_data_t const *cb_data) {
   msc_cbw_t const *cbw = cb_data->cbw;
   msc_csw_t const *csw = cb_data->csw;
@@ -63,5 +65,3 @@ void tuh_msc_umount_cb(uint8_t dev_addr) {
   (void) dev_addr;
   printf("A MassStorage device is unmounted\r\n");
 }
-
-#endif