LinuxKPI: timer KPI *_timer -> timer_*

del_timer() got renamed to timer_delete() approximately in Linux 6.2
(similar for *_sync and likely others).
Keep the old functions as compat; unclear when we can gc them.
We should also re-define them with a linuxkpi_ prefix to avoid possible
conflicts in the future if we do a full pass over this at some point.

Sponsored by: The FreeBSD Foundation (intiially)
MFC after: 3 days
X-MFC; preserve symbols, not inline
Reviewed by: dumbbell
Differential Revision: https://reviews.freebsd.org/D52074