[flang] Always resolve associate-name in select-type

Even if the selector expression has an error, we can resolve the
associate-name.

Original-commit: flang-compiler/f18@3c35c30f581b2ef0d7d74af8fddfc4adaba9d6c0
Reviewed-on: https://github.com/flang-compiler/f18/pull/281
Tree-same-pre-rewrite: false