Remove unused isZero function

[GMNGeoffrey]

Summary

Unused since https://reviews.llvm.org/D91503 and triggering
-Wunused-function

mlir/lib/Dialect/Linalg/Transforms/Fusion.cpp

for (auto operandIndex :
 
       fusableDependences[producerOp.getOperation()].push_back(
           *fusableDependence);
     }
   }
   return fusableDependences;
 }
 
-static bool isZero(Value v) {
-  if (auto cst = v.getDefiningOp<ConstantIndexOp>())
-    return cst.getValue() == 0;
-  return false;
-}
-
 /// Tile the fused loops in the root operation, by setting the tile sizes for
 /// all other loops to zero (those will be tiled later).
 static Optional<TiledLinalgOp> tileRootOperation(
     OpBuilder &builder, LinalgOp op, ArrayRef<Value> tileSizeVector,
     const LinalgTilingOptions &options, const std::set<unsigned> &fusedLoops) {
   SmallVector<Value, 4> tileSizes(tileSizeVector.begin(), tileSizeVector.end());
   auto zero = std_constant_index(0);
   for (unsigned i = 0, e = tileSizes.size(); i != e; ++i)