Revert " sched: Prevent wakeup to enter critical section needlessly"

This reverts commit 753e93cf6f9987e09b04d3faebd607e26e429e70.
Revert " timers: Avoid finding cpu for migration of running timers in __mod_ti…"

This reverts commit 638526539ce50807fc512a30f884cf10350a5db5.