Original commit message:

    [mips64] Remove a useless declaration of Operand.

    Change-Id: I5144d8315b5c1aca751d138e4d87240b703dc9e3
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3650359
    Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
    Auto-Submit: Yu Liu <liuyu@loongson.cn>
    Reviewed-by: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
    Cr-Commit-Position: refs/heads/main@{#80585}

Refs: v8/v8@3ebf205