i2c: Let the user specify PCI driver data through new_id

The i2c-amd756 and i2c-viapro drivers make use of the driver_data
field of the PCI device ID. When adding device IDs dynamically (by
writing to the new_id sysfs file) you cannot set the value of this
field by default. It has to be allowed explicitly. Do that, and
check the value so that the user can't crash the kernel accidentally.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>