staging: comedi: das16: remove a duplicate condition

We checked that "it->options[3]" was non-zero on the line before so
there is no need to check again.

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