staging: comedi: amplc_dio200: remove 'mainsize' from ISA boardinfo

All the ISA DIO200 boards have an i/o region size of 0x20 (DIO200_IO_SIZE).
Remove the boardinfo and open code the size in the comedi_request_region()
call.

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>