Implement << operator for DexRegisterLocation::Kind.

This makes it comparable in DCHECK_EQ and similar methods.

Change-Id: I6b5b237be89325850ae6860d011fd6741189ab01
diff --git a/runtime/check_reference_map_visitor.h b/runtime/check_reference_map_visitor.h
index b9ea475..fcf3326 100644
--- a/runtime/check_reference_map_visitor.h
+++ b/runtime/check_reference_map_visitor.h
@@ -100,8 +100,7 @@
           CHECK_EQ(location.GetValue(), 0);
           break;
         default:
-          LOG(FATAL) << "Unexpected location kind"
-                     << DexRegisterLocation::PrettyDescriptor(location.GetInternalKind());
+          LOG(FATAL) << "Unexpected location kind " << location.GetInternalKind();
       }
     }
   }