unix: remove extra trailing newlines in zsyscall_openbsd_*.go

These newlines are written by mksyscall.go but should not appear in the final
generated files once the output is passed through gofmt.  This is done by
mkall.sh but I had written a custom script just to generate these openbsd
zsyscall files in CL 468095.

Running the mksyscall.go output through gofmt fixes this issue.

Fixes golang/go#64820

Change-Id: I1b1bf55145bd5a5208e091ded24a973f953c479f
GitHub-Last-Rev: 514272b
GitHub-Pull-Request: #183
Reviewed-on: https://go-review.googlesource.com/c/sys/+/551715
Reviewed-by: Tobias Klauser <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>
Run-TryBot: Jorropo <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: jrick