Acquire a scratch register instead of passing scratch register
in JumpIfSmi and JumpIfNotSmi.

Change-Id: I21776e1cd9d19f0d55c25a5bb3f7efcc247c80e5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3135155Reviewed-by: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Auto-Submit: Liu yu <liuyu@loongson.cn>
Cr-Commit-Position: refs/heads/main@{#76632}