staging: comedi: icp_multi: remove n_aochan from boardinfo

There is only one board type supported by this driver and the
number of analog output channels is constant. Remove the
boardinfo for it and just open-code the value.

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