staging: comedi: das16: add a 'can_burst' flag to the private data

If the boardinfo 'size' is > 0x400 it indicates that the board has
additional registers that allow bursting of analog input data.

To better indicate this add a flag to the private data.

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>