[mlir][tosa] Check for unranked tensors during validation (#68509)

Fixes https://github.com/llvm/llvm-project/issues/67760
`levelCheckRank` ensures that the tensors for tosa operations are not
unranked

During tosa validation in `levelCheckRank`, we were trying to get the
rank of a tensor without checking if it is ranked or unranked, which
leads to an `assert` error. I see two ways to fix this:

- Only check `type.getRank() > tosa_level.MAX_RANK` if the tensor is
ranked, and then proceed as usual.
(like `if (type.hasRank() && type.getRank() > tosa_level.MAX_RANK)` , OR
- Throw an error for unranked tensors as result.