internal/syscall/unix: fix gofmt

internal/syscall/unix: fix gofmt

Change-Id: I24203c4e52bf4d55a6391d10fb4d30771c2674b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/518637
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>