Removing ifdef guards since our 4 supported architectures
implement this now.

Bug: v8:10971
Change-Id: Ic0295b1492a6316df61340a38f3e6d06d8fe64ed
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2620900
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72023}