Revert "LoongArch: Add swiotlb backups buffer"

LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7DWYY



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This reverts commit f728ed91.

Signed-off-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
(cherry picked from commit 39a3041a)