Backport f864e280b0f7 from the 7.3 MuQSS.

SMT topology masks retain offline siblings, so only reschedule active
CPUs in both sibling passes. Otherwise they can set NEED_RESCHED on an
idle task that is entering the CPU-dead path.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>