msm: ultrasound: control events from devices, conflicting with the USF.

In some UI frameworks there is no way to support
simultaneous digital pen and TSC input devices.
The acceptable solution is to disable the TSC
when the pen is close or touches the screen.
The USF can filter input events (e.g. TSC), produced by any driver.
This filtering is controlled by userland based events calculators.

Change-Id: If73adc8cb6039b037cb6a4aea148ac3326889f3c
Signed-off-by: Baruch Eruchimovitch <baruche@codeaurora.org>