io/i2c: flush after write

In time critical cases, waiting for the writes to be flushed results
in unexpected behavior.

Fixes golang/go#16155.

Change-Id: Ifb373fb2fd7daf272ffada31e11db8f307d8f93f
Reviewed-on: https://go-review.googlesource.com/24601
Reviewed-by: Blake Gentry <blakesgentry@gmail.com>
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>
1 file changed