add SUBTASK_EXIT in osal.h for TDD project

tinyusb/osal/osal.h

@@ -96,6 +96,8 @@ tusb_error_t osal_task_create(osal_task_t *task);
 #define OSAL_TASK_LOOP_BEGIN
 #define OSAL_TASK_LOOP_END
 
+#define SUBTASK_EXIT(error)   return error;
+
 //------------- Sub Task -------------//
 #define OSAL_SUBTASK_INVOKED_AND_WAIT(subtask, status) \
   status = subtask