arm64: smp: Add support for cpu park

hulk inclusion
category: feature
bugzilla: 48159
CVE: N/A

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

Introducing a feature of CPU PARK in order to save time
of cpus down and up during kexec, which may cost 250ms of
per cpu's down and 30ms of up.

As a result, for 128 cores, it costs more than 30 seconds
to down and up cpus during kexec. Think about 256 cores and more.

CPU PARK is a state that cpu power-on and staying in spin loop, polling
for exit chances, such as writing exit address.

Reserving a block of memory, to fill with cpu park text section,
exit address and park-magic-flag of each cpu. In implementation,
reserved one page for one cpu core.

Cpus going to park state instead of down in machine_shutdown().
Cpus going out of park state in smp_init instead of brought up.

One of cpu park sections in pre-reserved memory blocks,:
+--------------+
+ exit address +
+--------------+
+ park magic   +
+--------------+
+ park codes   +
+      .       +
+      .       +
+      .       +
+--------------+

Signed-off-by: Sang Yan <sangyan@huawei.com>
Reviewed-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>