staging: comedi: cb_pcidas: remove unnecessary check in caldac_8800_write()

The 'address' passed to this function is actually the comedi channel. This
value will always be less than the subdevice n_chan (which is 8). Remove
the unnecessary sanity check in caldac_8800_write().

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>