staging: comedi: addi_apci_1564: remove len_chanlist from di and do subdevices

This value is only needed for subdevices that support async commands.
The comedi core will default the value to 1 when it is not initialized.

Signed-off-by: Chase Southwood <chase.southwood@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>