staging: comedi: das1800: fix das-1801st-da boardinfo

The "da" type boards all have 4 analog outputs. Fix the boardinfo
for the das-1801st-da.

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>