As mentioned by http://www.microsoft.com/whdc/device/input/DigitizerDrvs_touch.mspx
multitouch devices are those that have the input report HID_CONTACTID.

This patch detects this and unloads the generic-usb driver.
Signed-off-by: NBenjamin Tissoires <benjamin.tissoires@enac.fr>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>