- arm64 aligns the frame, which guarantees an even
  number of return slots. Change RoundUp call to DCHECK.

Bug: v8:9198
Change-Id: I9a6949b93d14109f83f09800ffe75ebba6387b04
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2740481Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73274}