staging: comedi: ni_labpc: cleanup dev->board_name usage

The dev->board_name is initialized by the comedi core before calling
the (*attach) or (*auto_attach) functions. It only needs to be updated
if the driver does any additional probing and changes the dev->board_ptr.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>