stm32/usbdev: Make the USBD callback struct const so it can go in ROM.

ports/stm32/usbdev/class/inc/usbd_cdc_msc_hid.h

@@ -96,7 +96,7 @@ extern const uint8_t USBD_HID_MOUSE_ReportDesc[USBD_HID_MOUSE_REPORT_DESC_SIZE];
 
 extern const uint8_t USBD_HID_KEYBOARD_ReportDesc[USBD_HID_KEYBOARD_REPORT_DESC_SIZE];
 
-extern USBD_ClassTypeDef USBD_CDC_MSC_HID;
+extern const USBD_ClassTypeDef USBD_CDC_MSC_HID;
 
 // returns 0 on success, -1 on failure
 int USBD_SelectMode(uint32_t mode, USBD_HID_ModeInfoTypeDef *hid_info);

ports/stm32/usbdev/class/src/usbd_cdc_msc_hid.c

@@ -1112,7 +1112,7 @@ uint8_t USBD_HID_ClearNAK(USBD_HandleTypeDef *pdev) {
 }
 
 // CDC/MSC/HID interface class callback structure
-USBD_ClassTypeDef USBD_CDC_MSC_HID = {
+const USBD_ClassTypeDef USBD_CDC_MSC_HID = {
     USBD_CDC_MSC_HID_Init,
     USBD_CDC_MSC_HID_DeInit,
     USBD_CDC_MSC_HID_Setup,

ports/stm32/usbdev/core/inc/usbd_core.h

@@ -88,7 +88,7 @@ USBD_StatusTypeDef USBD_Init(USBD_HandleTypeDef *pdev, USBD_DescriptorsTypeDef *
 USBD_StatusTypeDef USBD_DeInit(USBD_HandleTypeDef *pdev);
 USBD_StatusTypeDef USBD_Start  (USBD_HandleTypeDef *pdev);
 USBD_StatusTypeDef USBD_Stop   (USBD_HandleTypeDef *pdev);
-USBD_StatusTypeDef USBD_RegisterClass(USBD_HandleTypeDef *pdev, USBD_ClassTypeDef *pclass);
+USBD_StatusTypeDef USBD_RegisterClass(USBD_HandleTypeDef *pdev, const USBD_ClassTypeDef *pclass);
 
 USBD_StatusTypeDef USBD_RunTestMode (USBD_HandleTypeDef  *pdev); 
 USBD_StatusTypeDef USBD_SetClassConfig(USBD_HandleTypeDef  *pdev, uint8_t cfgidx);

ports/stm32/usbdev/core/inc/usbd_def.h

@@ -235,7 +235,7 @@ typedef struct _USBD_HandleTypeDef
 
   USBD_SetupReqTypedef    request;
   USBD_DescriptorsTypeDef *pDesc;
-  USBD_ClassTypeDef       *pClass;
+  const USBD_ClassTypeDef *pClass;
   void                    *pClassData;  
   void                    *pUserData;    
   void                    *pData;    

ports/stm32/usbdev/core/src/usbd_core.c

@@ -155,7 +155,7 @@ USBD_StatusTypeDef USBD_DeInit(USBD_HandleTypeDef *pdev)
   * @param  pclass: Class handle
   * @retval USBD Status
   */
-USBD_StatusTypeDef  USBD_RegisterClass(USBD_HandleTypeDef *pdev, USBD_ClassTypeDef *pclass)
+USBD_StatusTypeDef  USBD_RegisterClass(USBD_HandleTypeDef *pdev, const USBD_ClassTypeDef *pclass)
 {
   USBD_StatusTypeDef   status = USBD_OK;
   if(pclass != 0)