tools/sched_ext: Handle migration-disabled tasks in scx_central

tools/sched_ext: Handle migration-disabled tasks in scx_central

When a task calls migrate_disable(), p->cpus_ptr is not updated until
migrate_disable_switch() runs during context switch, so dispatch_to_cpu()
may dequeue such a task and dispatch it to a CPU it cannot run on.

Extend the mismatch check in dispatch_to_cpu() to also test
is_migration_disabled() alongside the cpumask check, so tasks in this
window are bounced to the fallback DSQ.

Suggested-by: Andrea Righi <arighi@nvidia.com>
Suggested-by: Tejun Heo <tj@kernel.org>
Suggested-by: Kuba Piecuch <jpiecuch@google.com>
Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Reviewed-by: Kuba Piecuch <jpiecuch@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>