This looks good except that I found the commit message to be confusing. For instance, it is not true that all one link test runs will skip before this patch - they will in fact run. I do know what you mean of course but I think we should just be more clear.

I just modified the commit message to the below (ran the check scripts of course) and pushed. Thank you for the patch!

    dts: make one link the default topology
   
    Currently the default topology for test suites when not specified
    is two link. However, the majority of the DPDK functions tested
    in DTS can be tested with a single link. It is more intuitive for
    a testsuite or testcase lacking a topology decorator to default
    to the more basic requirement of 1 link, and force tests which
    really do require two link to include decorators explicitly
    saying so.

This is now applied to next-dts.