hrtimer: Keep track of first expiring timer per clock base

hrtimer: Keep track of first expiring timer per clock base

Evaluating the next expiry time of all clock bases is cache line expensive
as the expiry time of the first expiring timer is not cached in the base
and requires to access the timer itself, which is definitely in a different
cache line.

It's way more efficient to keep track of the expiry time on enqueue and
dequeue operations as the relevant data is already in the cache at that
point.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260224163431.404839710@kernel.org