LoongArch: fix two cpu hotplug problem

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8H1QC



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1. When cpu is hotplug out, cpu is in idle state and function
arch_cpu_idle_dead is called. Timer interrupt for this processor should
be disabled, else there will be timer interrupt for the dead cpu. Also
this prevents vcpu to schedule out during halt-polling flow when system
is running in vm mode, since there is pending timer interrupt.

This patch adds detailed implementation for timer shutdown interface, so
that timer will be disabled when cpu is plug-out.

2. for woken-up cpu, entry address is 8 bytes, we should check first low 4
bytes and then high 4 bytes.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>