Revert of PPC/s390: SmiUntag only for 32bit (patchset #1 id:1 of https://codereview.chromium.org/2842843005/ )

Reason for revert:
few tests are failing with stack overflow, will reland with the fix.

Original issue's description:
> PPC/s390: SmiUntag only for 32bit
>
> R=joransiu@ca.ibm.com, jyan@ca.ibm.com
> BUG=
> LOG=n
>
> Review-Url: https://codereview.chromium.org/2842843005
> Cr-Commit-Position: refs/heads/master@{#44908}
> Committed: https://chromium.googlesource.com/v8/v8/+/76dfdb7a32c4be41190ff6a01b23905976e5e0ff

TBR=joransiu@ca.ibm.com,jyan@ca.ibm.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review-Url: https://codereview.chromium.org/2852433002
Cr-Commit-Position: refs/heads/master@{#44936}