audio drivers: move util.{c,h} to generic directory

Change-Id: Ied0afa5ad9f66ee6f2249715d66fb62e6206d137
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7607
Reviewed-by: Alexander von Gluck <alex@terarocket.io>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>