libaudiohal@aidl: Fix 'stop' for MMap input streams

The current implementation of StreamHalAidl::stop was only
considering the output stream state machine. For input, these
is no need to drain, instead the framework can just flush
any remaining data. If the stream is draining, the framework
needs to drain until the stream enters standby (per the sync
input state machine).

Flag: EXEMPT bugfix
Bug: 419693182
Test: atest AAudioTests
Test: manual with Oboe Tester
Change-Id: Iac230e462889703079c72dcc9e436a0a1ea7f117