staging: comedi: das800: tidy up the private data

For aesthetic reasons, change the 'do_bits' type to unsigned int
to match the subdevice s->state. and change the 'forever' flag
to a bool.

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>