sw64: add memhotplug support for guest os

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56WV8



--------------------------------

This patch introduces memory-hotplug support for guest os, and it
should set CONFIG_KVM_MEMHOTLPUG=y on host to enable this feature.

Currently, only 1GB memory-hotplug granularity is supported, and
multiple granularity support will be implemented in the future.

Signed-off-by: Lu Feifei <lufeifei@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>