[SYCL][L0] retain event when taking a reference into a list (#4405)

Signed-off-by: Sergey V Maslov <[email protected]>

Author: smaslov-intel

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -5486,6 +5486,7 @@ pi_result piEnqueueMemBufferMap(pi_queue Queue, pi_mem Buffer,
   if (Event) {
     (*Event)->ZeCommandList = CommandList->first;
     CommandList->second.append(*Event);
+    PI_CALL(piEventRetain(*Event));
   }
 
   if (Buffer->MapHostPtr) {
@@ -5604,6 +5605,7 @@ pi_result piEnqueueMemUnmap(pi_queue Queue, pi_mem MemObj, void *MappedPtr,
   // Set the commandlist in the event
   (*Event)->ZeCommandList = CommandList->first;
   CommandList->second.append(*Event);
+  PI_CALL(piEventRetain(*Event));
 
   const auto &ZeCommandList = CommandList->first;
   if ((*Event)->WaitList.Length) {