Revert of PPC/s390: SmiUntag only for 32bit (patchset #1 id:1 of http…

…s://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}

src/builtins/ppc/builtins-ppc.cc

@@ -2208,9 +2208,7 @@ void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
   __ bind(&arguments_done);
 
   Label stack_empty, stack_done, stack_overflow;
-#if !V8_TARGET_ARCH_PPC64
   __ SmiUntag(r3);
-#endif
   __ sub(r3, r3, r5);
   __ cmpi(r3, Operand::Zero());
   __ ble(&stack_empty);

src/builtins/s390/builtins-s390.cc

@@ -2218,9 +2218,7 @@ void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
   __ bind(&arguments_done);
 
   Label stack_empty, stack_done, stack_overflow;
-#if !V8_TARGET_ARCH_S390X
   __ SmiUntag(r2);
-#endif
   __ SubP(r2, r2, r4);
   __ CmpP(r2, Operand::Zero());
   __ ble(&stack_empty);