HID: hid-multitouch: fix wrong protocol detection

The previous implementation introduced a randomness in the splitting
of the different touches reported by the device. This version is more
robust as we don't rely on hi->input->absbit, but on our own structure.

This also prepares hid-multitouch to better support Win8 devices.

[Jiri Kosina <jkosina@suse.cz>: fix build]

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