nr: fix compilation warning

openair2/RRC/NR/rrc_gNB_nsa.c

@@ -118,6 +118,10 @@ void rrc_parse_ue_capabilities(gNB_RRC_INST *rrc, LTE_UE_CapabilityRAT_Container
   rrc_add_nsa_user(rrc,ue_context_p, m);
 }
 
+/* generate prototypes for the tree management functions (RB_INSERT used in rrc_add_nsa_user) */
+RB_PROTOTYPE(rrc_nr_ue_tree_s, rrc_gNB_ue_context_s, entries,
+             rrc_gNB_compare_ue_rnti_id);
+
 void rrc_add_nsa_user(gNB_RRC_INST *rrc,struct rrc_gNB_ue_context_s *ue_context_p, x2ap_ENDC_sgnb_addition_req_t *m) {
   // generate nr-Config-r15 containers for LTE RRC : inside message for X2 EN-DC (CG-Config Message from 38.331)
   rrc_gNB_carrier_data_t *carrier=&rrc->carrier;