sched_ext: Fix dsq_local_on selftest

sched_ext: Fix dsq_local_on selftest

The dsp_local_on selftest expects the scheduler to fail by trying to
schedule an e.g. CPU-affine task to the wrong CPU. However, this isn't
guaranteed to happen in the 1 second window that the test is running.
Besides, it's odd to have this particular exception path tested when there
are no other tests that verify that the interface is working at all - e.g.
the test would pass if dsp_local_on interface is completely broken and fails
on any attempt.

Flip the test so that it verifies that the feature works. While at it, fix a
typo in the info message.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ihor Solodrai <ihor.solodrai@pm.me>
Link: http://lkml.kernel.org/r/Z1n9v7Z6iNJ-wKmq@slm.duckdns.org
Signed-off-by: Tejun Heo <tj@kernel.org>