audio_effects.conf - Add loudness enhancer

This was added to the default audio_effects.conf in KitKat, but
the DSPManager override still doesn't have it.

Change-Id: I7dbc97fb76a188df385d2e73c769b7aade9baa82
New icon
[2/3] Bass boost: Center frequency
[2/3] Stereo widener
Boeffla Sound Control