PPC: [runtime] Drop redundant %CharFromCode runtime entry.

Port 2b4cb2a1

Original commit message:
    The %StringCharFromCode and %CharFromCode runtime function perform
    exactly the same task, so we need only one of them.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1429953005

Cr-Commit-Position: refs/heads/master@{#31904}

src/crankshaft/ppc/lithium-codegen-ppc.cc

@@ -4769,7 +4769,8 @@ void LCodeGen::DoDeferredStringCharFromCode(LStringCharFromCode* instr) {
   PushSafepointRegistersScope scope(this);
   __ SmiTag(char_code);
   __ push(char_code);
-  CallRuntimeFromDeferred(Runtime::kCharFromCode, 1, instr, instr->context());
+  CallRuntimeFromDeferred(Runtime::kStringCharFromCode, 1, instr,
+                          instr->context());
   __ StoreToSafepointRegisterSlot(r3, result);
 }
 

src/ppc/code-stubs-ppc.cc

@@ -2885,7 +2885,7 @@ void StringCharFromCodeGenerator::GenerateSlow(
   __ bind(&slow_case_);
   call_helper.BeforeCall(masm);
   __ push(code_);
-  __ CallRuntime(Runtime::kCharFromCode, 1);
+  __ CallRuntime(Runtime::kStringCharFromCode, 1);
   __ Move(result_, r3);
   call_helper.AfterCall(masm);
   __ b(&exit_);