staging: comedi: addi_apci_1564: board does not have analog outputs

The board supported by this driver does not have analog outputs.  Remove
the subdevice init for it.

Signed-off-by: Chase Southwood <chase.southwood@gmail.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>