hwmon: convert it87 to platform driver

This is the patch for converting it87 to a platform driver (and remove i2c-isa).

Signed-off-by: Corentin LABBE <corentin.labbe@geomatys.fr>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>