Suppress more UNUSED warnings (#14466)

Marlin/src/HAL/HAL_DUE/MarlinSerialUSB_Due.cpp

 
 // Public Methods
 void MarlinSerialUSB::begin(const long baud_setting) {
+  UNUSED(baud_setting);
 }
 
 void MarlinSerialUSB::end() {

Marlin/src/HAL/HAL_DUE/usb/sd_mmc_spi_mem.cpp

 }
 
 bool sd_mmc_spi_unload(bool unload) {
+  UNUSED(unload);
   return true;
 }
 

Marlin/src/HAL/HAL_DUE/usb/usb_task.c

   bool usb_task_msc_isenabled(void)             { return main_b_msc_enable; }
 #endif
 
-bool usb_task_cdc_enable(const uint8_t port)  { return ((main_b_cdc_enable = true)); }
-void usb_task_cdc_disable(const uint8_t port) { main_b_cdc_enable = false; main_b_dtr_active = false; }
+bool usb_task_cdc_enable(const uint8_t port)  { UNUSED(port); return ((main_b_cdc_enable = true)); }
+void usb_task_cdc_disable(const uint8_t port) { UNUSED(port); main_b_cdc_enable = false; main_b_dtr_active = false; }
 bool usb_task_cdc_isenabled(void)             { return main_b_cdc_enable; }
 
 /*! \brief Called by CDC interface
  * Callback running when CDC device have received data
  */
-void usb_task_cdc_rx_notify(const uint8_t port) { }
+void usb_task_cdc_rx_notify(const uint8_t port) { UNUSED(port); }
 
 /*! \brief Configures communication line
  *
  */
 static uint16_t dwDTERate = 0;
 void usb_task_cdc_config(const uint8_t port, usb_cdc_line_coding_t *cfg) {
-    // Store last DTE rate
-    dwDTERate = cfg->dwDTERate;
+  UNUSED(port);
+  // Store last DTE rate
+  dwDTERate = cfg->dwDTERate;
 }
 
-
 void usb_task_cdc_set_dtr(const uint8_t port, const bool b_enable) {
-
+  UNUSED(port);
   // Keep DTR status
   main_b_dtr_active = b_enable;