FROMGIT: tick/broadcast: Program wakeup timer when entering idle if required

When configuring the broadcast timer on entry to and exit from deep idle
states, prefer a per-CPU wakeup timer if one exists.

On entry to idle, stop the tick device and transfer the next event into
the oneshot wakeup device, which will serve as the wakeup from idle. To
avoid the overhead of additional hardware accesses on exit from idle,
leave the timer armed and treat the inevitable interrupt as a (possibly
spurious) tick event.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-5-will@kernel.org


(cherry picked from commit ea5c7f1b tip/tip.git timers/core)
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 185092876
Change-Id: I62a49231e213285f95e9f0cf6a07633984930b56