This includes adding a padding slot to the stack handler, which is done for all
architectures for consistency.

Bug: v8:6644
Change-Id: I8a6379a82e2a9d1819069850b6734489bd6071a6
Reviewed-on: https://chromium-review.googlesource.com/822477Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#50070}