Allow for any default vibration intensity level.

Because we can't always create the range of effects we'd like, we may
need different default intensity levels for different devices. This
works fine for prebaked effects, but for application defined amplitudes
we need to provide a scaling function. In addition, this scaling
function should leave amplitude values untouched in the default state so
that application developers produce the effects they expect.

Bug: 80275800
Test: manual
Merged-In: Ibb552ddfa60891853ebcb1a5567ed6745bb5defe
Change-Id: Ibb552ddfa60891853ebcb1a5567ed6745bb5defe