[crankshaft] Remove the useless HCallStub instruction.

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

Index: src/crankshaft/ppc/lithium-codegen-ppc.cc
diff --git a/src/crankshaft/ppc/lithium-codegen-ppc.cc b/src/crankshaft/ppc/lithium-codegen-ppc.cc
index 91e664963ffb7c9d86e504eb221ab4f64f73f2e8..387218f3fca91abafcf38ef94a32362301280fc9 100644
--- a/src/crankshaft/ppc/lithium-codegen-ppc.cc
+++ b/src/crankshaft/ppc/lithium-codegen-ppc.cc
@@ -890,26 +890,6 @@ void LCodeGen::DoParameter(LParameter* instr) {
 }
 
 
-void LCodeGen::DoCallStub(LCallStub* instr) {
-  DCHECK(ToRegister(instr->context()).is(cp));
-  DCHECK(ToRegister(instr->result()).is(r3));
-  switch (instr->hydrogen()->major_key()) {
-    case CodeStub::RegExpExec: {
-      RegExpExecStub stub(isolate());
-      CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
-    case CodeStub::SubString: {
-      SubStringStub stub(isolate());
-      CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
-    default:
-      UNREACHABLE();
-  }
-}
-
-
 void LCodeGen::DoUnknownOSRValue(LUnknownOSRValue* instr) {
   GenerateOsrPrologue();
 }