MdeModulePkg DxeCore: Fix a memory leak in InstallMemoryAttributesTable()

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

MdeModulePkg/Core/Dxe/Misc/MemoryAttributesTable.c

@@ -174,6 +174,8 @@ InstallMemoryAttributesTable (
     }
     MemoryMap = NEXT_MEMORY_DESCRIPTOR(MemoryMap, DescriptorSize);
   }
+  MemoryMap = MemoryMapStart;
+  FreePool (MemoryMap);
 
   Status = gBS->InstallConfigurationTable (&gEfiMemoryAttributesTableGuid, MemoryAttributesTable);
   ASSERT_EFI_ERROR (Status);