staging: comedi: me4000: remove unnecessary Step 2b test in (*do_cmdtest)

This test is unnecessary. It covers all the possible combinations of the
scan_end_src and stop_src triggers so the final else can never be reached.

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>