padconf: add am335x registers

Change-Id: I5ea50a243f3847d5cdea291caae0fb4be93b2f20
include: Import dev/i2c/i2c_io.h

Change-Id: Icb754891349b7f571863f3a87b0318c28c35ac79
i2c: work in progress i2c dirver for am335x/dm37xx

Change-Id: I78fff3f5360a45ab53bf058f06e64dd088295787