- BTrain requires to set more parameters than just tx/rx_data_width
- it would be messy to have all the parameters in the top of each board
- I made a record with all tx/rx parameters and replaced the currently
  existing two generics that reach the top of svec/spec/vfchd_board
  with these record.
- Now, all the tx/rx parameters of tx/rx streamers can be set when
  using the "board" top
- Default constant is used with default values (defined ine streamers pkg)
- it is planed to have constant with default parameters for BTrain as well
  in the BTrain package. Possibly, the same policy can be used for other
  applications