Linux 6.2/6.15: del_timer_sync() renamed to timer_delete_sync()

Renamed in 6.2, and the compat wrapper removed in 6.15. No signature or
functional change apart from that, so a very minimal update for us.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Pavel Snajdr <snajpa@snajpa.net>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17229