io/i2c: document the test case fields; test against a 10-bit addr

Change-Id: Id4dabd60fdadf22fcde414d107d3c07e0dbcb842
Reviewed-on: https://go-review.googlesource.com/22620
Reviewed-by: Johan Euphrosine <proppy@google.com>
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>
1 file changed