Use a dedicated lock for last queued command set/get

Change-Id: If3d2144841c7863cf7afe2ca85aea62e0a3a33c7

rocclr/platform/commandqueue.hpp

@@ -126,6 +126,7 @@ class CommandQueue : public RuntimeObject {
         rtCUs_(rtCUs),
         priority_(priority),
         queueLock_("CommandQueue::queueLock"),
+        lastCmdLock_("LastQueuedCommand"),
         device_(device),
         context_(context),
         cuMask_(cuMask){}
@@ -134,6 +135,7 @@ class CommandQueue : public RuntimeObject {
   uint rtCUs_;                        //!< The number of used RT compute units
   Priority priority_;                 //!< Queue priority
   Monitor queueLock_;                 //!< Lock protecting the queue
+  Monitor lastCmdLock_;               //!< Lock protecting the last queued command
   Device& device_;                    //!< The device
   SharedReference<Context> context_;  //!< The context of this command queue
   const std::vector<uint32_t>& cuMask_;  //!< The CU mask