internal/syscall/unix: correct fchmodat on openbsd
This is incorrectly calling the fchownat trampoline - call fchmodat
as intended.
Change-Id: I7b1e758d456006303ca95b70df9e6b52d3020158
Reviewed-on: https://go-review.googlesource.com/c/go/+/649655 Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Damien Neil <dneil@google.com> Reviewed-by: Damien Neil <dneil@google.com>
Commit-Queue: Damien Neil <dneil@google.com>
Auto-Submit: Damien Neil <dneil@google.com>