Reapply "timers: Rename del_timer_sync() to timer_delete_sync()"

This reverts commit 5f29666f.

It causes merge conflicts in 6.1.91.  Will be brought back after that
merge happens.

Change-Id: I2b6335bf5296d51bd08f92816aa1c98c92b822a8
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>