st3m: partial usb unfucking

I have returned from the USB mines bearing great news.

The badge should now get less stuck when doing CDC comms.

Apparently, TinyUSB does not attempt to flush its CDC TX FIFO unless you
request it or unless it just finished another transfer.

components/st3m/st3m_console.c

@@ -145,16 +145,6 @@ void st3m_gfx_splash(const char *c);
 // Called by st3m_usb_cdc when it has the opportunity to send some data to the
 // host.
 size_t st3m_console_cdc_on_txpoll(uint8_t *buffer, size_t bufsize) {
-    // I have no idea why this is needed, but it is. Otherwise a large backlog
-    // of data cuases the IN endpoint to get stuck.
-    //
-    // I've spend three days debugging this.
-    //
-    // No, I'm not fine. Thanks for asking, though. I appreciate it.
-    if (bufsize > 0) {
-        bufsize -= 1;
-    }
-
     int64_t now = esp_timer_get_time();
 
     xSemaphoreTake(_state.mu, portMAX_DELAY);

components/st3m/st3m_usb_cdc.c

@@ -46,6 +46,7 @@ void st3m_usb_cdc_txpoll(void) {
     for (;;) {
         uint32_t space = tud_cdc_n_write_available(st3m_usb_interface_app_cdc);
         if (space == 0) {
+            tud_cdc_n_write_flush(st3m_usb_interface_app_cdc);
             return;
         }