include: Import dev/i2c/i2c_io.h

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

Change-Id: I6e0b2e9f700f0d0ac3772e485d637045045b50bb
Importing usr.sbin/i2cscan

Change-Id: If33144ba70400d24369308b7644abefb4438c9db