Implement PDCP reset counters for reestablishment

After a reestablishment, the PDCP sequence number counters have to be
reset. Implement an API to allow the RRC to reset the sequence numbers
for a particular UE in the case of reestablishment

openair2/RRC/NR/rrc_gNB.c

@@ -1238,6 +1238,7 @@ void rrc_gNB_generate_RRCReestablishment(const protocol_ctxt_t *ctxt_pP,
                               kRRCenc,
                               kRRCint,
                               kUPenc);
+  nr_pdcp_reestablishment(ctxt_pP->rntiMaybeUEid);
 
   if (!NODE_IS_CU(rrc->node_type)) {
     apply_macrlc_config_reest(rrc, ue_context_pP, ctxt_pP, ctxt_pP->rntiMaybeUEid);