only reset SDU buffer in RLC AM/UM

lib/src/upper/rlc_am.cc

@@ -72,14 +72,6 @@ rlc_am::~rlc_am()
 {
   // reset RLC and dealloc SDUs
   stop();
-
-  if(rx_sdu) {
-    pool->deallocate(rx_sdu);
-  }
-
-  if(tx_sdu) {
-    pool->deallocate(tx_sdu);
-  }
 }
 
 void rlc_am::init(srslte::log                 *log_,

lib/src/upper/rlc_um.cc

@@ -136,11 +136,11 @@ void rlc_um::reset()
   vr_uh    = 0;
   pdu_lost = false;
   if(rx_sdu) {
-    pool->deallocate(rx_sdu);
+    rx_sdu->reset();
   }
 
   if(tx_sdu) {
-    pool->deallocate(tx_sdu);
+    tx_sdu->reset();
   }
 
   if(mac_timers) {