HID: hid-multitouch: minor fixes based on additional review

* amended Kconfig (PixCir and Hanvon are the same panel but with
  different name)
* insert field name in mt_class and retrieving it in mt_probe
* add 2 quirks: MT_QUIRK_VALID_IS_INRANGE, MT_QUIRK_VALID_IS_CONFIDENCE,
  in order to find the field "valid"
* inlined slot_is_contactid and slot_is_contact_number
* cosmetics changes (tabs and comments)
* do not send unnecessary properties once the touch is up

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>