i2c-i801: Don't probe for slaves on IDF channels

I don't know if Fujitsu is ever going to produce Patsburg-based
machines, but if they do, I'd rather not probe the secondary (IDF)
SMBus channels. At least not until we have a good reason for doing so.

On a side note, I'm not even sure if it is right to enable detection
of HWMON and DDC devices on the IDF channels. Time will tell...

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>