fix limited UL data throughput in do-ra mode

In case of noS1-mode, we initialize the 'logicalChannelBearer_exist' array element for the pre-configured DRB0 in function 'nr_l2_init_ue()'.
That array is indexed with the LCID.
For DRB0, the LCID is 4.
Unfortunately, the code incorrectly used the array at index 0.
Therefore, the UE sent neither scheduling requests nor buffer status reports, what resulted in extremely poor UL throughput.

openair2/LAYER2/NR_MAC_UE/main_ue_nr.c

@@ -81,7 +81,7 @@ NR_UE_MAC_INST_t * nr_l2_init_ue(NR_UE_RRC_INST_t* rrc_inst) {
         nr_pdcp_layer_init();
         nr_pdcp_add_drbs(ENB_FLAG_NO, nr_ue_mac_inst->crnti, 0, rbconfig->drb_ToAddModList, 0, NULL, NULL, &rlc_bearer_list);
         nr_rlc_add_drb(nr_ue_mac_inst->crnti, rbconfig->drb_ToAddModList->list.array[0]->drb_Identity, rlc_rbconfig);
-        nr_ue_mac_inst->logicalChannelBearer_exist[0] = true;
+        nr_ue_mac_inst->logicalChannelBearer_exist[4] = true;
 
         // free memory
         free_nr_noS1_bearer_config(&rbconfig, &rlc_rbconfig);