Fix QNX build error

[Hoverbear]

Description

As noted in https://github.com/rust-lang/libc/pull/4609/files#r2607712816, on *-nto-qnx710 the codebase seems to currently fail to compile:

error: type `types::Padding<i32>` is more private than the item `neutrino::ClockPeriod`
    --> src/unix/nto/neutrino.rs:1244:5
     |
1244 | /     pub fn ClockPeriod(
1245 | |         __id: crate::clockid_t,
1246 | |         _new: *const crate::_clockperiod,
1247 | |         __old: *mut crate::_clockperiod,
1248 | |         __reserved: Padding<c_int>,
1249 | |     ) -> c_int;
     | |_______________^ function `neutrino::ClockPeriod` is reachable at visibility `pub`
     |
note: but type `types::Padding<i32>` is only usable at visibility `pub(crate)`
    --> src/types.rs:17:1
     |
  17 | pub(crate) struct Padding<T: Copy>(MaybeUninit<T>);
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     = note: `-D private-interfaces` implied by `-D warnings`
     = help: to override `-D warnings` add `#[allow(private_interfaces)]`

I believe the change from that PR may have been inadvertent given the other contents.

Sources

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI
  • This failed with

    cargo:rustc-link-search=native=/home/ana/git/rust-lang/libc/target/x86_64-pc-nto-qnx710/debug/build/libc-test-ae02735b35db6470/out
  
  --- stderr
  
  thread 'main' panicked at ctest/src/ffi_items.rs:141:25:
  not implemented: Foreign functions are unlikely to have any other pattern.
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace