LoongArch: kdump: Add high memory reservation

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7A8UR



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Reserve high memory for the capture kernel to avoid kdump operation failure
on 3C5000 machines with old firmware.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Change-Id: Iacf0c56b2cdb86e66dd7568168e1c97e472c4e3a
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
(cherry picked from commit d7b62011)