HID: multitouch: correct eGalax a001 protocol

This device use another protocol while sending the events.
It's the same as the one described as "serial" by Microsoft.
We are keeping here the sn_move and sn_pressure parameters for
egalax devices.

CC: Cedric Sodhi <manday@gmx.net>
CC: Chris Bagwell <chris@cnpbagwell.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>