audio: Rename hw/audio/audio.h to hw/audio/soundhw.h

All the functions in hw/audio/audio.h are called "soundhw_*()"
and live in hw/audio/audiohw.c. Rename the header file for
consistency.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Hervé Poussineau <hpoussin@reactos.org>
Message-id: 20170508205735.23444-4-ehabkost@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>