io/i2c: add an example for Open

Change-Id: Ie9ad7a09b91f53372107dae19cb01dfd09978a94
Reviewed-on: https://go-review.googlesource.com/22517
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Johan Euphrosine <proppy@google.com>
1 file changed