io/i2c, io/spi: test examples when not linux

Change-Id: I79ac1ad797eecc7d07674cec72eda203de88aed5
Reviewed-on: https://go-review.googlesource.com/24851
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Matt Aimonetti <mattaimonetti@gmail.com>
2 files changed