arm64: Add CPU hotplug support

hulk inclusion
category: feature
bugzilla: 20208
CVE: NA
---------------------------

To support CPU hotplug, we need to implement 'acpi_(un)map_cpu()' and
'arch_(un)register_cpu()' for ARM64. These functions are called in
'acpi_processor_hotadd_init()/acpi_processor_remove()' when the CPU is hot
added into or hot removed from the system.

Note: This patch only support core hotplug and does not support socket
hotplug because we don't support live configuration of GIC.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Acked-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>