[flang] [llvm] [flang][NFC] Restore I/O runtime API header name (PR #132423)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur approved this pull request.

LGTM, altough I think inline should be avoided for larger functions to reduce compile time and I don't see how it  could cause confusion. If header name confusion is an issue, the bigger issue is that we have many headers with the same name. We have four different `Allocatable.h`/`allocatable.h`, five `tools.h` and five `Utils.h`.

https://github.com/llvm/llvm-project/pull/132423