Move the recently introduced extra check for 32-bit platforms so
that it covers all code paths that would be hit by custom/future
memory limit settings.

Bug: chromium:1057094
Change-Id: I5e2217a24578ee82c7bfa753b7d5dcd3d00e1b7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2083300Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66568}