staging: comedi: drivers: set dev->board_name before attaching

The comedi (*attach) and (*auto_attach) functions are used to attach
legacy and PnP type devices to the comedi subsystem. If we can set the
dev->board_name before doing the attach, the drivers will not have to
worry about doing it.

Drivers that do additional probing can still change the dev->board_name
if necessary.

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