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>
diff --git a/driver/driver_freebsd.go b/driver/driver_bsd.go
similarity index 91%
rename from driver/driver_freebsd.go
rename to driver/driver_bsd.go
index 23aa3bd..51020f5 100644
--- a/driver/driver_freebsd.go
+++ b/driver/driver_bsd.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//+build dragonfly freebsd netbsd openbsd
+
 package driver
 
 const rssMultiplier = 1
diff --git a/driver/driver_unix.go b/driver/driver_unix.go
index ec05eee..797e5d7 100644
--- a/driver/driver_unix.go
+++ b/driver/driver_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package driver