staging: comedi: pcl711: add AI cancel handler
staging: comedi: pcl711: add AI cancel handler

Comedi subdevices that support asynchronous commands should have a
'cancel' handler to stop an in-progress command.  Add such a handler to
the pcl711 driver module.  I think merely setting the acquisition mode
to "software-triggered" would be sufficient, but also clear the
interrupt status for good luck.

Signed-off-by: Ian Abbott <9e6ba6483b6a3e14d61f7c987e72ecb5b46122d6@mev.co.uk>
Reviewed-by: H Hartley Sweeten <382ff55d8e07d1082d179e669636cd1552da4f36@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs