This reverts commit dfdc3135.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> PPC/s390: [interpreter] correctly advance over debug scaling prefixes.
> 
> Port 7a07d74b
> 
> R=​yangguo@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
> BUG=
> LOG=N
> 
> Change-Id: I99553fde819cbdc8a12df5b82d9d7230ba4ef8b3
> Reviewed-on: https://chromium-review.googlesource.com/1042355
> Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
> Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
> Cr-Commit-Position: refs/heads/master@{#52970}

TBR=yangguo@chromium.org,michael_dawson@ca.ibm.com,jyan@ca.ibm.com,joransiu@ca.ibm.com

Change-Id: I04fadaa81a6dd124811c002ab4ffa61e3785b717
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1043025Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#52971}