Reimplement nFAPI message exchange after msgDataTx removal

Reimplement nFAPI message exchange between L1 and L2 following the
changes in parent commit removing msgDataTx.

Avoid direct calls and use NR_IF_module fptrs to avoid linking problems.
allowing to remove some function definitions that are not needed.

nfapi/open-nFAPI/pnf/public_inc/nfapi_pnf_interface.h

@@ -856,7 +856,7 @@ int nfapi_pnf_p7_start(nfapi_pnf_p7_config_t* config);
  */
 int nfapi_pnf_p7_stop(nfapi_pnf_p7_config_t* config);
 
-/*! NR Slot indication
+/*! NR get stuff
  * message copied from nfapi_pnf_p7_subframe_ind
  * \param config A pointer to a PNF P7 config
  * \param phy_id The phy_id for the phy instance
@@ -868,8 +868,14 @@ int nfapi_pnf_p7_stop(nfapi_pnf_p7_config_t* config);
  *
  * If messages are not in the subframe buffer, they dummy subframe messages will be sent
  */
-int nfapi_pnf_p7_slot_ind(nfapi_pnf_p7_config_t* config, uint16_t phy_id, uint16_t sfn, uint16_t slot);
-
+int nfapi_pnf_p7_get_msgs(nfapi_pnf_p7_config_t* config,
+                          uint16_t phy_id,
+                          uint16_t sfn,
+                          uint16_t slot,
+                          nfapi_nr_dl_tti_request_t* ret_dl_tti,
+                          nfapi_nr_ul_tti_request_t* ret_ul_tti,
+                          nfapi_nr_ul_dci_request_t* ret_ul_dci,
+                          nfapi_nr_tx_data_request_t* ret_tx_data);
 
 /*! Subframe indication
  * \param config A pointer to a PNF P7 config