audio_route: fix possible segfault

* Mixers may not allocate memory to save their values if the type is not
  of bool, enum, or int. However we do not check the type when actually
  attempting to use the allocated memory, resulting in possibly writing
  into random memory.

Change-Id: I8e59c8e6211b7ea10bd128069378632e0ced27a5
[1/3] AudioEffects: Add center frequency param to bassboost

Change-Id: Ia47a3f679a82392232b33b72e8dbd3b2545ee109
[2/3] audio_effects: Add a stereo widening effect

Change-Id: I0dd68fef857e8a031f52a63a81c642cb930419c6