[XLA] Move a CHECK into Layout verification

Sparse layouts that specify tiling should fail verification, not CHECK-fail in ToString.

PiperOrigin-RevId: 233483254

tensorflow/compiler/xla/layout_util.cc

@@ -247,6 +247,10 @@ Layout CreateDefaultLayoutForRank(int64 rank) {
       }
       dimensions_in_layout[dim] = true;
     }
+  } else {
+    if (layout.tiles_size() != 0) {
+      return InvalidArgument("Only dense layouts can be tiled.");
+    }
   }
 
   return Status::OK();