It was just an add used only in one place, so I inlined it.

I also noticed that some methods were using scratch registers as
parameters but didn't really need to do so.

Bug: v8:7703
Change-Id: Ia1e5570d478673cb0835cff97e3a37d9a35c60a6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1924266Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65097}