Input: wacom - BTN_TOOL_DOUBLETAP is not a valid device_type

It is replaced by BTN_TOOL_FINGER.

Signed-off-by: Ping Cheng <pingc@wacom.com>
Tested-by: Rafi Rubin <rafi@seas.upenn.edu>
Reviewed-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>