PPC: Load from PropertyCells using PropertyCell::kValueOffset rather than Cell::kValueOffset

Port dda2bd6f

Original commit message:

R=mbrandy@us.ibm.com, svenpanne@chromium.org, danno@chromium.org, jkummerow@chromium.org

BUG=

Review URL: https://codereview.chromium.org/1028323002

Cr-Commit-Position: refs/heads/master@{#27387}

src/ic/ppc/handler-compiler-ppc.cc

@@ -722,7 +722,7 @@ Handle<Code> NamedLoadHandlerCompiler::CompileLoadGlobal(
   Register result = StoreDescriptor::ValueRegister();
   Handle<WeakCell> weak_cell = factory()->NewWeakCell(cell);
   __ LoadWeakValue(result, weak_cell, &miss);
-  __ LoadP(result, FieldMemOperand(result, Cell::kValueOffset));
+  __ LoadP(result, FieldMemOperand(result, PropertyCell::kValueOffset));
 
   // Check for deleted property if property can actually be deleted.
   if (is_configurable) {