i2c: Try 12.8 MHz

* Well 14.4 MHz slightly increase battery and had no issues.  Let's go down a little bit more!

Change-Id: Ib0ee1cd8a724052f3dbc6a7e4a59ada47bf8a4d3
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>