floss: Refine the naming and variable init

This is mainly to facilitate future refactor and development.

- Make naming more specific
- Move the variable declaration closer to the usage

Bug: 235901463
Tag: #floss
Test: system/gd/cert/run & Build and verify HFP works
Change-Id: Ia158929534c7eb23889ef359d2d5b373adf844a1