Revert "libaudiohal@aidl: Make IHalAdapterVendorExtension mandatory"

Revert submission 2929484-fix-b-321651892-ihaladapter

Reason for revert: possible cause of b/323385784

Reverted changes: /q/submissionid:2929484-fix-b-321651892-ihaladapter

Change-Id: Ifaafeec27bee08648a3ced6d507b99454c317692
11 files changed