This reverts commit 50baf934.

Reason for revert: breaks arm64 nosnap debug tests:

https://build.chromium.org/p/client.v8.ports/builders/V8%20Linux%20-%20arm64%20-%20sim%20-%20nosnap%20-%20debug/builds/8418

Original change's description:
> [arm64] Switch jssp to csp
> 
> Switch stack pointer to using csp directly, making jssp redundant.
> 
> Bug: v8:6644
> Change-Id: I8e38eda50d56a25161b187c0a033608dd9f90239
> Reviewed-on: https://chromium-review.googlesource.com/860097
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
> Cr-Commit-Position: refs/heads/master@{#50487}

TBR=martyn.capewell@arm.com,bmeurer@chromium.org

Change-Id: I20015885e6029271ee6558509cdb92ff1a106e5f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6644
Reviewed-on: https://chromium-review.googlesource.com/860319Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50488}