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>

drivers/hid/hid-multitouch.c

@@ -311,6 +311,7 @@ static void mt_feature_mapping(struct hid_device *hdev,
 			*quirks |= MT_QUIRK_ALWAYS_VALID;
 			*quirks |= MT_QUIRK_IGNORE_DUPLICATES;
 			*quirks |= MT_QUIRK_HOVERING;
+			*quirks |= MT_QUIRK_CONTACT_CNT_ACCURATE;
 			*quirks &= ~MT_QUIRK_NOT_SEEN_MEANS_UP;
 			*quirks &= ~MT_QUIRK_VALID_IS_INRANGE;
 			*quirks &= ~MT_QUIRK_VALID_IS_CONFIDENCE;