alsa_sound: change voice-call stop sequence

When application processor is paired with an external modem, stop
command should be sent to the DSP on the modem before closing the
Slimbus channels on the application processor.

Bug: 7313016
Change-Id: Ibafeaf9a9badbf32cc955c4e8b5c81e5efdcbb0c
Signed-off-by: Iliyan Malchev <malchev@google.com>