floss: Clean up btm_route_sco_data

- Make btm_msbc_zero_frames and hfp_msbc_decoder_decode_packet output
  const.
- Replace memcpy with std:copy

Bug: 232463744
Tag: #floss
Test: Build and verify with devices supporting WBS
Change-Id: Ide4604c7cb589e834d7c59ba228e07011b866ca6