HID: multitouch: fix Win8 protocol for Sharp like devices

The Sharp LC-20FE1-W screen (04dd:9681) behaves like the Nexio 42".
It may report out of ranges values that are filtered out by relying
on the Contact Count HID field.
Adding the quirk MT_QUIRK_CONTACT_CNT_ACCURATE makes hid-multitouch
strongest against this kind of device, without breaking the current
devices.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>