audiopolicy: engine: use apm XML config file for volume curves

This CL removes the hard coded volume table in the engine and
use as a fallback for compatibility reason the apm config file
to load the volume tables.

Bug: 124767636
Test: dumpsys media.audio_policy & diff with previous version

Change-Id: I0392aad730c67ee79f898093fd1b4f64e26ab3fd
Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>