USB HID: Add ID for eGalax Multitouch used in JooJoo tablet

The JooJoo tablet (http://thejoojoo.com/) contains an "eGalax Inc. USB
TouchController", and this patch hooks it up to the egalax-touch driver.
Without the patch we don't get any cursor motion, since it comes through
Z/RX rather than X/Y.

(The egalax-touch driver does not yet generate a correct event sequence
for the "serial" protocol used by this device, though -- see the note
added to the code, which comes from research by Stéphane Chatty.)

Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Stéphane Chatty <chatty@enac.fr>
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>