Add padding above arguments, as part of JSSP removal.

Bug: v8:6644
Change-Id: Iee03c3c8cd6da3d62b0b4c86a12400a5fdfe99de
Reviewed-on: https://chromium-review.googlesource.com/757136Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#49374}