ue,mac_nr: reset DL and UL HARQ when MAC is reset

DL and UL harq entities where never reset when the UE was going into IDLE.
As a result, the first transmissions where always using the old softbuffer
without resetting it, resulting in wrong TB being decoded.

In the case of the RAR, the UE decoded a wrong (in fact the old) TCRNTI
and the RA procedure failed.

srsue/src/stack/mac_nr/mac_nr.cc

@@ -103,6 +103,16 @@ void mac_nr::reset()
   proc_sr.reset();
   proc_ra.reset();
   mux.reset();
+  for (const auto& cc : dl_harq) {
+    if (cc != nullptr) {
+      cc->reset();
+    }
+  }
+  for (const auto& cc : ul_harq) {
+    if (cc != nullptr) {
+      cc->reset();
+    }
+  }
 }
 
 void mac_nr::run_tti(const uint32_t tti)