[crankshaft] Remove the useless HAllocateBlockContext instruction.

src/crankshaft/ppc/lithium-ppc.cc

Index: src/crankshaft/ppc/lithium-ppc.cc
diff --git a/src/crankshaft/ppc/lithium-ppc.cc b/src/crankshaft/ppc/lithium-ppc.cc
index a71092a8a6df86b9cf5f24ac817b4b2eca1f9bf4..c959cbccd555a96be936aa544c71735d1c24f417 100644
--- a/src/crankshaft/ppc/lithium-ppc.cc
+++ b/src/crankshaft/ppc/lithium-ppc.cc
@@ -2553,14 +2553,5 @@ LInstruction* LChunkBuilder::DoStoreFrameContext(HStoreFrameContext* instr) {
   return new (zone()) LStoreFrameContext(context);
 }
 
-
-LInstruction* LChunkBuilder::DoAllocateBlockContext(
-    HAllocateBlockContext* instr) {
-  LOperand* context = UseFixed(instr->context(), cp);
-  LOperand* function = UseRegisterAtStart(instr->function());
-  LAllocateBlockContext* result =
-      new (zone()) LAllocateBlockContext(context, function);
-  return MarkAsCall(DefineFixed(result, cp), instr);
-}
 }  // namespace internal
 }  // namespace v8