staging: comedi: pcl812: remove unneeded tests in pcl812_ai_cmdtest

The step 2 tests to make sure that the triggers are unique is not
needed for single source triggers. These were already trivially
validated in step 1.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>