audio_hal_interface: Pass a2dp_offload_enabled flag to bluetooth::audio::a2dp::init

Removes the dependecy from audio_hal_interface on
  - btif_av_is_a2dp_offload_enabled

Bug: 365022887
Test: m com.android.btservices
Flag: EXEMPT, no logical change
Change-Id: I835baafdf83e14762d548b286e45457fa9e39387