LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB

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The perf events infrastructure of LoongArch is very similar to old MIPS-
based Loongson, so most of the codes are derived from MIPS.
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>