driver: allow to build for all BSDs

Add appropriate build tags in order to allow building the driver for all
BSDs supported by Go.

Change-Id: I9f97051c6dbd85a8c00798cfa94fed90504c4fcb
Reviewed-on: https://go-review.googlesource.com/77472
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2 files changed