arm64: kdump: Don't force page-level mappings for memory above 4G

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I545H8


CVE: NA

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If the crashkernel reservation is deferred, such boundaries are not known
when the linear mapping is created. But its upper limit is fixed, cannot
above 4G. Therefore, unless otherwise required, block mapping should be
used for memory above 4G to improve performance.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>