Ultrasound: Filter out the special key event for digital pen hovering cursor

Ultrasound hovering cursor uses a special key event. This event is relevant
only for the InputReader that shows/hides the cursor accordingly.
Therefore, if the event  is sent from the ultrasound device it is filtered
out in the InputReader and is not sent to applications.

Change-Id: Id3a9718be6bdb144e80bfa32c0a18a9900071167
1 file changed