[mlir][tensor] Fix FoldTensorCastProducerOp for multiple result operations (#93374)

For patterns where there are multiple results apart from dpsInits, this
fails.
E.g.:
```
%13:2 = iree_codegen.ukernel.generic "iree_uk_unpack"
ins(%extracted_slice : tensor<?x1x16x16xf32>) outs(%11 :
tensor<?x?xf32>) ... -> tensor<?x?xf32>, i32
``` 
The above op has results apart from dpsInit and hence fails. The PR
assumes that the result has dpsInits followed by nonDpsInits.