base: audiofx: harden against offload effects

Hack for now to allow using DSPManager for offload effects

-offload effect equalizer has only 5 bands but DSPManager has hardcoded 6
-offload effect bassboost doesnt support center freq

Change-Id: I9ad661221654415b2be3ed18f8cf31453d6df637
Merge remote-tracking branch 'omni/android-4.4' into android-4.4