i2c: i801: Improve handling platform data for tco device

The platform data structures are used in the respective i801_add_tco
functions only. Therefore we can make the definitions local to these
functions.

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>