SWDEV-485827 release initial_heap_buffer_

This PR adds the initialization and release of initial_heap_buffer_
to prevent memory leaks.

Change-Id: I4ab8721b439a1a3a6f6e53d63d870e572f7c984a

rocclr/device/device.cpp

@@ -649,6 +649,7 @@ Device::Device()
       blitProgram_(nullptr),
       context_(nullptr),
       heap_buffer_(nullptr),
+      initial_heap_buffer_(nullptr),
       arena_mem_obj_(nullptr),
       vaCacheAccess_(nullptr),
       vaCacheMap_(nullptr),
@@ -662,6 +663,11 @@ Device::~Device() {
     heap_buffer_ = nullptr;
   }
 
+  if (initial_heap_buffer_ != nullptr) {
+    delete initial_heap_buffer_;
+    initial_heap_buffer_ = nullptr;
+  }
+
   if (arena_mem_obj_ != nullptr) {
     arena_mem_obj_->release();
   }