fix nr-ru.c external declarations in .c file

The external declarations were incorrect, leading to mismatching
prototypes of config_ru and config_rru (true bug in OAI lte!).

radio/COMMON/common_lib.h

@@ -567,12 +567,11 @@ struct openair0_device_t {
    * \param idx RU index
    * \param arg pointer to capabilities or configuration
    */
-  void (*configure_rru)(int idx, void *arg);
+  void (*configure_rru)(void *, void *arg);
 
-/*! \brief Pointer to generic RRU private information
+  /*! \brief Pointer to generic RRU private information
    */
 
-
   void *thirdparty_priv;
 
   /*! \brief Callback for Third-party RRU Initialization routine