io/i2c: add a no-implementation of devfs for !linux

Allow users to build with Devfs on all platforms by exporting required
symbols with no implementation.
Users can use tools such as goimports even if their host machine is not linux.

Change-Id: Iad6db0272daaceec788b455885b7ef1aeb39284f
Reviewed-on: https://go-review.googlesource.com/23890
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>
1 file changed