Rename the kNone enum in SimdPrefix to kNoPrefix

R=adamk@chromium.org

Bug: v8:12244
Change-Id: I8604dfadea24ce5f00c710de4d3c38da9d8a27a7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3182886Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77064}