Add function for scaling haptic data.

The function was in AudioMixer. With adding haptic-generating effect,
there will be more than one place calling the scaling function. In that
case, it makes more sense to put the scaling function in vibrator
library.

Bug: 136490803
Test: play audio-coupled-haptic files
Test: play audio with attaching haptic-generating effect
Change-Id: Ia7f88463e2d2b7f11954ab9bb6aeff8191c78894