Audio: Fix Visualizer's get/set parameter methods not worked bug

To LiquidSmooth dev team.

I found a bug of Visualizer class and fixed it on RootBox ROM (*). And I noticed that the LiquidSmooth also has the same issue. This bug affects to audio visualization apps such as...
- Music Visualizer (https://play.google.com/store/apps/details?id=com.h6ah4i.android.music_visualizer2&hl=en)
- Audio Glow Music Visualizer (https://play.google.com/store/apps/details?id=com.cyphercove.audioglowfs&hl=en)
- projectM Music Visualizer (https://play.google.com/store/apps/details?id=com.psperl.projectM&hl=en)

(*) https://github.com/Root-Box/frameworks_av/pull/1

Thanks, 
Haruki Hasegawa (h6a h4i)