staging: comedi: adv_pci1724: remove ao_range_list_1724

All the AO channels have the same ranges. Remove the subdevice
s->range_table_list and just use the s->range_table to setup the
ranges.

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>