staging: comedi: dyna_pci10xx: Set number of AO channels to 1

The "dyna_pci10xx" driver supports the Dynalog India PCI-1050.  There
seems to be very little online information available about this card,
but as far as I can tell[*], it only has 1 AO (analog output) channel,
not 16 AO channels as reported in the Comedi subdevice information.
Besides, the Comedi "insn_write" handler for the AO subdevice takes no
account of channel numbers.  Change the `n_chans` member of the AO
subdevice structure to 1 to reflect this.

[*] The card is no longer mentioned on the manufacturer's web-site and I
couldn't find any archived page for the site on archive.org.  I found
part of a scientific paper which describes the card as having a single
channel D/A converter:
<http://shodhganga.inflibnet.ac.in/bitstream/10603/150646/15/15_chapter%205.pdf

>.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>