staging: comedi: amplc_dio200: set board_name before common attach

`dio200_common_attach()` is called from `dio200_attach()` for ISA boards
and from `dio200_auto_attach()` for PCI boards.  `dio200_auto_attach()`
assigns `dev->board_name` (where `dev` is the `struct comedi_device *`
under consideration) before calling `dio200_common_attach()`.  Do the
same in `dio200_attach()` so it can be used there before the call to
`dio200_common_attach()`.  This makes the assignment in
`dio200_common_attach()` unnessary, so remove the assignment from there.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>