This reverts commit c2f25454.

Reason for revert: CFI build failures: https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux%20-%20arm64%20-%20sim%20-%20CFI/11255/overview

Original change's description:
> Avoid use of x18 register on arm64
>
> This causes crashes on Windows, as x18 is the "platform register",
> holding a pointer to thread-local storage.
>
> R=​jkummerow@chromium.org
> CC=​seth.brenith@microsoft.com
>
> Bug: v8:12959
> Change-Id: I20b8bee145d4ab3a40d8d140d98572df8300251c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3695569
> Reviewed-by: Seth Brenith <seth.brenith@microsoft.com>
> Commit-Queue: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#81090}

Bug: v8:12959
Change-Id: Id239ccb55e0a2d29051f402af64a855a8fd2d23b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3702231
Owners-Override: Leszek Swirski <leszeks@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#81091}