staging: comedi: das1800: use CMDF_ROUND_...

Replace use of the `TRIG_ROUND_...` macros with the new names
`CMDF_ROUND_...`.  The numeric values are unchanged.

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