timers-urgent-2022-04-17

  - Fix the warning condition in __run_timers() which does not take into
    account, that a CPU base (especially the deferrable base) has never a
    timer armed on it and therefore the next_expiry value can become stale.

  - Replace a WARN_ON() in the NOHZ code with a WARN_ON_ONCE() to prevent
    endless spam in dmesg.

  - Remove the double star from a comment which is not meant to be in
    kernel-doc format.