changing CFG_TUD_CDC from 1 -> 0 compile issues

### Operating System

Windows 10

### Arduino IDE version

2.3.4

### Board

Feather M0 adalogger (SAMD21)

### ArduinoCore version

1.8.5

### TinyUSB Library version

3.4.1

### Sketch as ATTACHED TXT

-

### Compiled Log as ATTACHED TXT

several compile issue. Really sorry I didn't keep them, but easy to reproduce and probably a little expected. More constructive info below.

### What happened ?

-

### How to reproduce ?

To the motivation: between CFG_TUD_CDC==0 and the CFG_TUD_HID==1 (I changed them at the same time. shouldn't have ...) I save 7kB to flash so I felt it was worth reporting.
Sorry, my TinyUSB library code is a little butchered by now, so I can't make a pretty pull request. But here are the fixes (all via #if/#endif).

Adafruit_tinyUSB.h, line 40: (this fixes a C linkage error)
```
#if CFG_TUD_CDC
#include "arduino/Adafruit_USBD_CDC.h"
#else
#include "Adafruit_TinyUSB_API.h" // usually, Adafruit_USBD_CDC.h would include this. but without CFG_TUD_CDC ...
#endif
```

Adafruit_USBD_Device.cpp, line 273. must prevent access to SerialTinyUSB
```
#if CFG_TUD_CDC
SerialTinyUSB.begin(115200);
#endif
```

Adafruit_TinyUSB_API.cpp, line 53. Keep body of FlushCDC empty
```
#if CFG_TUD_CDC
uint8_t const cdc_instance = Adafruit_USBD_CDC::getInstanceCount();
for (uint8_t instance = 0; instance < cdc_instance; instance++) {
tud_cdc_n_write_flush(instance);
}
#endif
```

Just my suggestions. Hope this helps.

### Debug Log

_No response_

### Screenshots

_No response_

Reproduce the compile failures on the Feather M0 with CFG_TUD_CDC set to 0, then inspect the conditional paths in Adafruit_tinyUSB.h around line 40, Adafruit_USBD_Device.cpp around line 273, and Adafruit_TinyUSB_API.cpp around line 53. Confirm the suggested guards resolve compilation without CDC while preserving the existing CDC-enabled build.

Written by the indexing model from the issue text.