Save memory (move usb mass storage buffer to reusableBuffer) (#5579)

* Save 128 byte by moving variable to stack

* Make usb mass storage buffer smaller on F2 processors and put into reuseablebuffer

- Lower USB mass storage buffer to 512 bytes per default on F2
  targets, makes usb speed slightly slower ~600 kB/s instead ~700 KB/s
  in my tests, saving 3584 bytes
- Save another ~300 bytes by putting that buffer into reusableBuffer

* Don't put id into reusuableBuffer

All uses of id can be on the stack as well. Makes no difference for ram usage but makes it safer to reuse reusableBuffer

* Only link cdc serial when needed

We always linked usb cdc even in non debug builds. CDC uses about ~600 byte of RAM for its buffers and structures.

radio/src/main_arm.cpp

@@ -58,7 +58,7 @@ void handleUsbConnection()
 #endif
       POPUP_MENU_START(onUSBConnectMenu);
     }
-    if (g_eeGeneral.USBMode != USB_UNSELECTED_MODE) {
+    if (g_eeGeneral.USBMode != USB_UNSELECTED_MODE && g_eeGeneral.USBMode <= USB_MAX_MODE) {
       setSelectedUsbMode(g_eeGeneral.USBMode);
     }
   }