HID: multitouch: cleanup with eGalax PID definitions

This is just a renaming of USB_DEVICE_ID_DWAV_EGALAX_MULTITOUCH{N}
to USB_DEVICE_ID_DWAV_EGALAX_MULTITOUCH_{PID} to handle more eGalax
devices.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>