staging: comedi: quatech_daqp_cs: fix daqp_ai_cancel()

Make sure interrupts are disabled and the event flags are cleared when
an analog input async command is canceled.

Remove the unnecessary calls to stop any running conversions in the
(*insn_read) and (*do_cmd) functions. The comedi core will only call
these functions if the subdevice is not busy (it has already been
canceled).

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>