[lib/ObjectYAML] - Fix BB after r353607 [2]. NFC.

The second and the last place it seems.

Error was:
[  4%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/Error.cpp.o
/Users/buildslave/as-bldslv9_new/lld-x86_64-darwin13/llvm.src/lib/ObjectYAML/ELFYAML.cpp:993:15: error: unused variable 'Object' [-Werror,-Wunused-variable]
  const auto *Object = static_cast<ELFYAML::Object *>(IO.getContext());

llvm-svn: 353609

Author: George Rimar

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -990,8 +990,7 @@ struct NormalizedMips64RelType {
 
 void MappingTraits<ELFYAML::DynamicEntry>::mapping(IO &IO,
                                                    ELFYAML::DynamicEntry &Rel) {
-  const auto *Object = static_cast<ELFYAML::Object *>(IO.getContext());
-  assert(Object && "The IO context is not initialized");
+  assert(IO.getContext() && "The IO context is not initialized");
 
   IO.mapRequired("Tag", Rel.Tag);
   IO.mapRequired("Value", Rel.Val);