Revert "only reset SDU buffer in RLC AM/UM"

This reverts commit 8d852ddfe5.

This commit was needed because the order in which objects
where destructed on UE exit was such that the byte_buffer was deleted
before RLC_AM dtor was called.

lib/src/upper/rlc_am.cc

@@ -72,6 +72,14 @@ 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) {
-    rx_sdu->reset();
+    pool->deallocate(rx_sdu);
   }
 
   if(tx_sdu) {
-    tx_sdu->reset();
+    pool->deallocate(tx_sdu);
   }
 
   if(mac_timers) {