LoongArch: Remove unused variables

mainline inclusion
from mainline-v5.19
commit 3a3a4f7a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB


CVE: NA

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There are some variables never used or referenced, this patch
removes these varaibles and make the code cleaner.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>