[mlir] cleanup transform payload setting

Before the multi-handle relaxation, the transform interpreter did not
actually set payload for a handle that had no further uses as a hacky
mechanism to work around the multi-handle problem. This is no longer
necessary and can be removed to avoid debugging surprises when a handle
has no payload even when its producing op assigned it.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D135585

mlir/lib/Dialect/Transform/IR/TransformInterfaces.cpp

@@ -66,10 +66,6 @@ transform::TransformState::setPayloadOps(Value value,
   assert(value != kTopLevelValue &&
          "attempting to reset the transformation root");
 
-  // TODO: this may go now
-  if (value.use_empty())
-    return success();
-
   auto iface = value.getType().cast<TransformTypeInterface>();
   DiagnosedSilenceableFailure result =
       iface.checkPayload(value.getLoc(), targets);