Input: wacom_serial4 - add support for Wacom ArtPad II tablet

Tablet initially begins communicating at 9600 baud, so this command
should be used to connect to the device:

    $ inputattach --daemon --baud 9600 --wacom_iv /dev/ttyS0

https://github.com/linuxwacom/xf86-input-wacom/issues/40



Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>