HID: multitouch: support arrays for the split of the touches in a report

Win8 certification introduced the ability to transmit two X and two Y per
touch. The specification precises that it must be used in an array.

This test guarantees that we split the touches on the last element
in this array.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-multitouch.c

@@ -576,12 +576,15 @@ static int mt_event(struct hid_device *hid, struct hid_field *field,
 			return 0;
 		}
 
-		if (usage->hid == td->last_slot_field)
-			mt_complete_slot(td, field->hidinput->input);
-
-		if (field->index == td->last_field_index
-			&& td->num_received >= td->num_expected)
-			mt_sync_frame(td, field->hidinput->input);
+		if (usage->usage_index + 1 == field->report_count) {
+			/* we only take into account the last report. */
+			if (usage->hid == td->last_slot_field)
+				mt_complete_slot(td, field->hidinput->input);
+
+			if (field->index == td->last_field_index
+				&& td->num_received >= td->num_expected)
+				mt_sync_frame(td, field->hidinput->input);
+		}
 
 	}