bugfix: nr: free RA process when UE is removed

The bug was:
connect a phone, disconnect, repeat five times. The fifth time the phone
does not reconnect because there is no free RA process.

When an UE is removed, we have to free associated RA processes.

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c

@@ -1705,6 +1705,7 @@ void mac_remove_nr_ue(module_id_t mod_id, rnti_t rnti)
 {
   int UE_id;
   int i;
+  int cc_id;
   NR_UE_info_t *UE_info = &RC.nrmac[mod_id]->UE_info;
 
   for (i = 0; i < MAX_MOBILES_PER_GNB; i++) {
@@ -1741,6 +1742,20 @@ void mac_remove_nr_ue(module_id_t mod_id, rnti_t rnti)
     rnti_to_remove_count++;
     if (pthread_mutex_unlock(&rnti_to_remove_mutex)) exit(1);
   }
+
+  /* clear RA process(es?) associated to the UE */
+  for (cc_id = 0; cc_id < NFAPI_CC_MAX; cc_id++) {
+    NR_COMMON_channels_t *cc = &RC.nrmac[mod_id]->common_channels[cc_id];
+    for (i = 0; i < NR_NB_RA_PROC_MAX; i++) {
+      if (cc->ra[i].rnti == rnti) {
+        LOG_D(MAC, "free RA process %d for rnti %d\n", i, rnti);
+        /* is it enough? */
+        cc->ra[i].cfra  = false;
+        cc->ra[i].rnti  = 0;
+        cc->ra[i].crnti = 0;
+      }
+    }
+  }
 }
 
 uint8_t nr_get_tpc(int target, uint8_t cqi, int incr) {