cid-form ops.enable() now hands the task's cmask to the scheduler and
set_cmask() repeats it right after. Add a cid-form selftest that checks both
against p->cpus_ptr, that they match each other, that the initial
set_cmask() lands before set_weight() and before the task first becomes
runnable, and that set_cmask() never precedes enable(), across class-switch
enables, fork-path enables and live affinity changes.
v2: Mismatch details returned through a caller-local struct instead of
globals, alloc_words validated in the header check, loop bounded by nr_cids
directly (Andrea Righi).
Signed-off-by: Tejun Heo <[email protected]>