staging: comedi: addi_apci_3120: don't reset board when canceling ai command

The analog input (*cancel) stops the async command. There is not reason to also
call the board reset function.

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>