Removed unused code related to Audio, A2DP Sink and Video

* Function BTA_AvEnable_Sink() - never used
  - Event BTA_AV_API_SINK_ENABLE_EVT
  - Processing function bta_av_api_sink_enable()
  - AVDT_SINK_Activate() and AVDT_SINK_Deactivate() : not used anymore

* A2DP SINK related functions that are only declared:
  - btif_queue_focus_request()
  - audio_focus_status()

* Audio-related function that is never used:
  - bta_av_sbc_cfg_for_cap()

* Video-related functions that are only declared:
  - bta_av_co_video_src_data_path()
  - bta_av_co_video_setconfig()
  - bta_av_co_video_open()
  - bta_av_co_video_close()
  - bta_av_co_video_start()
  - bta_av_co_video_report_conn()
  - bta_av_co_video_report_rr()
  - bta_av_co_video_delay()
  - bta_av_co_video_disc_res()
  - bta_av_co_video_getconfig()
  - bta_av_co_video_stop()

Change-Id: I0c0c80578ab2675d2fe23dea3f11b2a0d82283f0