Cleanup in the bta/av layer

* Removed unused defines and function declarations
* Removed unused tBTA_AV_Q_INFO.vdp
* Cleanup of some of the log messages

Also:
* Added constant AVDT_TSEP_INVALID instead of using a hard-coded value

Change-Id: I9ce7b5b08dec7c9ea9699d9f6c598acb39fb105a