Now that hid-generic ignores all win7 compatible multitouch devices, this patch
allows hid-multitouch to catch them.  The idea is to rely on the quirk
HID_QUIRK_MULTITOUCH to drop the device if no ContactID is given.

There is the need for a blacklist here as other devices may need a special
driver (ntrig for instance).
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>