Configure complete PDCP in lte-(ue)softmodem

* Instead of partly initializing in read_config_and_init(), everything of
  PDCP is initialized in main() of lte-softmodem
* Omit RC.rrc access in RRU through checking of RC.nb_inst > 0
* Includes FlexRAN, i.e. do not start FlexRAN in RRU
* Function pointers to PDCP functions have to be set explicitly (avoid
  confusion of multiply setting function pointers)

openair2/LAYER2/PDCP_v10.1.0/pdcp.c

@@ -2175,9 +2175,6 @@ uint64_t pdcp_module_init( uint64_t pdcp_optmask ) {
       netlink_init();
     }
   }
-
-  /* default interface with rlc (will be modified if CU) */
-  pdcp_set_rlc_funcptr((send_rlc_data_req_func_t)rlc_data_req, (pdcp_data_ind_func_t) pdcp_data_ind);
   return pdcp_params.optmask ;
 }