A node's future-hotplug memory range starts from very high end normally, e.g. 
1TB, and is not continuous with its current existing memory range. It should not 
be covered by the global variable 'nodes' as it assumes the node's memory is 
continuous. Otherwise it can make nodes' memory ranges become very big and 
overlapped, and populate_memnodemap() fails.

We can ignore future-hotplug memory range for now. Physical memory hotplug 
support in future will handle it.

Signed-off-by: Yang Xiaowei <xiaowei.yang@intel.com>

Thanks,
Xiaowei