floss: Add HFP hal

Add an HFP hal with stubbed defaults for Android and a complete
implementation for Floss that queries the kernel apis. Follow-up CLs
will integrate this into the stack.

Bug: 223685328
Tag: #floss
Test: Ran on Floss and verified HAL initializes with correct values.

Change-Id: I797646db2caef475aa77bbfb71616d82ea98d05c