frameworks/av: 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) Commit ID: d64a966f40b05f514312291b2e43b6e7c475845c

    frameworks/media: Fix aliasing violations

  (*2) Commit ID: 350adb3460dfa29eac5e34c3e2a90cf5011ce3d4

    EffectVisualizer: Fix aliasing violations

Change-Id: I5fcef8d958108bf442b96d7726069f82ffbfe49c