[mlir][sparse] add linalg elt-wise fusion to sparsifier pipeline (#90924)

yields better IR in general, and all end-to-end tests pass!

Author: aartbik

mlir/lib/Dialect/SparseTensor/Pipelines/SparseTensorPipelines.cpp

@@ -31,8 +31,9 @@
 
 void mlir::sparse_tensor::buildSparsifier(OpPassManager &pm,
                                           const SparsifierOptions &options) {
-  // Rewrite named linalg ops into generic ops.
+  // Rewrite named linalg ops into generic ops and apply fusion.
   pm.addNestedPass<func::FuncOp>(createLinalgGeneralizeNamedOpsPass());
+  pm.addNestedPass<func::FuncOp>(createLinalgElementwiseOpFusionPass());
 
   // Sparsification and bufferization mini-pipeline.
   pm.addPass(createSparsificationAndBufferizationPass(