Also remove remnants of x87 port.

Change-Id: I3376539504d2a04c9f918ab39d0976eaca31782f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3097866
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76313}