[mlir][linalg] ComprehensiveBufferize: Do not copy InitTensorOp results

E.g.:

```
%2 = memref.alloc() {alignment = 128 : i64} : memref<256x256xf32>
%3 = memref.alloc() {alignment = 128 : i64} : memref<256x256xf32>

// ... (%3 is not written to)

linalg.copy(%3, %2) : memref<256x256xf32>, memref<256x256xf32>
vector.transfer_write %11, %2[%c0, %c0] {in_bounds = [true, true]} : vector<256x256xf32>, memref<256x256xf32>
```

Avoid copies of %3 if %3 came directly from an InitTensorOp.

Differential Revision: https://reviews.llvm.org/D109742

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

@@ -2190,6 +2190,7 @@ static LogicalResult bufferize(OpBuilder &b, VectorTransferOpInterface op,
     newInputBuffer = createNewAllocDeallocPairForShapedValue(
         b, loc, writeOp.source(), aliasInfo);
     Value v = lookup(bvm, writeOp.source());
+    if (!isInitTensorOp(writeOp.source()))
       b.create<CopyOp>(loc, v, newInputBuffer);
   } else {
     // InPlace write will result in memref.tensor_load(x) which must