dt-bindings: i2c: Add P8 OCC hwmon device documentation

Document the bindings for I2C-based OCC hwmon device.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>