Changeset 834a86fe in rtems for cpukit/score

score: Restrict affinity for EDF SMP scheduler

The SMP EDF scheduler supports a one-to-one and one-to-all thread to
processor affinity. It accepted affinity sets which are a proper
subset of the online processor containing at least two processors owned by
the scheduler. In this case it used a one-to-one thread to processor
affinity. This leads to undefined behaviour if a processor is removed
since the higher level check in rtems_scheduler_remove_processor() does
not account for this implementation detail.

Restrict the affinity set accepted by the SMP EDF scheduler to

1. all online processors, or

2. exactly one processor owned by the scheduler.

Close #4545.