HID: multitouch: add support for Nexio 42" panel

This device is the worst device I saw. It keeps TipSwitch and InRange
at 1 for fingers that are not touching the panel.
The solution is to rely on the field ContactCount, which is accurate
as the correct information are packed at the begining of the frame.

Unfortunately, CountactCount is most of the time at the end of the report.
The solution is to pick it when we have the whole report in raw_event.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 34e2547..8311380 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -597,6 +597,9 @@
 #define USB_VENDOR_ID_NEC		0x073e
 #define USB_DEVICE_ID_NEC_USB_GAME_PAD	0x0301
 
+#define USB_VENDOR_ID_NEXIO		0x1870
+#define USB_DEVICE_ID_NEXIO_MULTITOUCH_420	0x010d
+
 #define USB_VENDOR_ID_NEXTWINDOW	0x1926
 #define USB_DEVICE_ID_NEXTWINDOW_TOUCHSCREEN	0x0003