audio: Initialize LPA variables in audioflinger

 - During initialization of audioflinger, a number of
variables related to LPA are not set to default values.
This causes an undesired side effect that the first
effect in the effect chain is considered to be LPA
enabled. Since LPA does not execute effect processing,
switching xLoud on/off does nothing.
 - Fixed by initializing member variables in audioflinger.

Change-Id: Ide06fb0e6804558388e6610cc7686f168591e4a5