HID: hid-multitouch: Send events per slot if CONTACTCOUNT is missing

The recent capacitive DWAV firmwares do not use the CONTACTCOUNT
field, and the touch frame boundary can therefore not be determined.
This patch makes the driver report the touch frame at each completed
slot instead.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>