hack: reuse same rbBitmap for DL retransmission

The libscheduler does not return a correct rbBitmap
(as far as I understand).

Let's memorize the one used for 1st transmission and reuse it.

If there are two or more UEs in the system then things may
fail if the scheduler allocates the PRBs used by UE 1 in 1st
transmission to UE 2 at the same time of a retransmission for
UE 1.

openair2/LAYER2/MAC/eNB_scheduler.c

@@ -712,6 +712,7 @@ static int fixed_size(int lcid)
  * in the meantime, this array stores the latest mcs used for each rnti/harq_pid
  */
 static unsigned char latest_mcs[65536][10];
+static unsigned int latest_rbbitmap[65536][10];
 
 /* TODO: deal with more than one transport block */
 static void fapi_schedule_retransmission_ue(int module_id, int CC_id, int frame, int subframe, struct BuildDataListElement_s *d)
@@ -773,6 +774,7 @@ printf("RETR rnti %d rbBitmap %x rbShift %d rbgSubset %d resAlloc %d nr_of_tbs %
    * in the meantime, let's replace with the last used MCS
    */
   d->dci.mcs[0] = latest_mcs[d->rnti][d->dci.harqProcess];
+  d->dci.rbBitmap = latest_rbbitmap[d->rnti][d->dci.harqProcess];
 
   fapi_convert_dl_dci(module_id, CC_id, &d->dci, a);
 #if MEGALOG
@@ -879,6 +881,7 @@ printf("RUN fapi_schedule_ue\n");
    * in the meantime, we store the latest used mcs for each rnti/harq_pid
    */
   latest_mcs[d->rnti][d->dci.harqProcess] = d->dci.mcs[0];
+  latest_rbbitmap[d->rnti][d->dci.harqProcess] = d->dci.rbBitmap;
 
   tbs = d->dci.tbsSize[0] / 8;