When do memory hotplug, if there is numa node, we should add
the memory size to the corresponding node memory size.

It affects the result of hmp command "info numa".
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>