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

This commit fixes broken Visualizer's get/set parameter methods.
The bug was introduced by modifications to avoid complilation errors.(*1,*2)

(*1) 91b6deea4562bbec7713f6796a6ecff200424832

    frameworks/media: Fix aliasing violations

(*2) bf935694368da97e79004b8197a5f6f2e9460c11

    EffectVisualizer: Fix aliasing violations
Merge pull request #2 from h6ah4i/bugfix_audioeffect_visualizer

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