MFC: r249203 (partial)

- Make ata_str2mode() static, it's not used outside of ata-all.c.
- Move ata_timeout() to ata-all.c so we don't need to expose both this
  function and ata_cam_end_transaction() but only the former.
- Move ata_cmd2str() from ata-queue.c to ata-all.c.
- Add some missing prototypes.