io/i2c: export ResolveAddr

Third party driver implementations need to know whether the address
is 10-bit or not. They also need the original address.

Change-Id: I6bebdddf4821c3dd57a9e049cdc59314d487e0f2
Reviewed-on: https://go-review.googlesource.com/23360
Reviewed-by: Minux Ma <minux@golang.org>
3 files changed