MIPS: Octeon: Add I2C platform device.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
To: linux-i2c@vger.kernel.org
To: ben-linux@fluff.org
To: khali@linux-fr.org
Cc: Rade Bozic <rade.bozic.ext@nsn.com>
Patchwork: http://patchwork.linux-mips.org/patch/847/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>