Resolved hardware error observed during SCO Connection setup

Hardware error was caused due to a faulty HCI command formed in the
process of vendor specific pre-SCO setup in the stack(set_audio_state)

Fixed the above problem and also added back the vendor (interface)
mapping for the set_audio_state functionality to facilitate the
sending of the pre-SCO vendor specific commands.

Made common vendor library audio setting by moving to hci subsystem.

General cleanup around this functionality.

Bug: 19923226
Change-Id: I4a743f6725459f360bd2a90e0a46f08fcca2292d