staging: comedi: addi_common.h: remove 'b_AiContinuous' from private data

This member of the private data can be determined by checking the cmd->stop_src.
Do that instead.

Fix the b_AiContinuous check in apci3120_ai_cmd(). The (*do_cmdtest) validates
that the cmd->stop_arg os >= 1 for TRIG_COUNT and 0 for TRIG_NONE. The correct
test to set this flag is (cmd->stop_src == TRIG_NONE).

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>