x86/kdump: make crash kernel boot faster

euleros inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8RJ6X?from=project-issue


CVE: NA

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If other cpus offline before handle the crash NMI, the
waiting_for_crash_ipi can not be decreased to 0, and
current cpu will wait 1 second. So break if all other
cpus offline.

Signed-off-by: zhangnaichuan <zhangnaichuan@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>