i2c: i801: Document Intel DNV and Broxton

Add missing entries into i2c-i801 documentation and Kconfig about recently
added Intel DNV and Broxton.

Reported-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>