configs: copy bike_bell.wav for specific targets

- Removes general bike_bell.wav copy statement to
  avoid copying to all target variants (for e.g.,
  GVM).
- Adds bike_bell.wav for only msmnile_au and
  msmsteppe_au to be copied onto targets.

Change-Id: I85eecda9fa6019d4703b8ac2938602041e12167d
3 files changed