CVE-2026-74512: audit: fix potential use-after-free in audit_del_rule()

In the Linux kernel, the following vulnerability has been resolved: audit: fix potential use-after-free in audit_del_rule() `audit_del_rule()` destroys `e->rule.exe` via `audit_remove_mark_rule()` before unlinking the rule from RCU-visible filter lists and waiting for a grace period. Concurrent readers in `audit_filter()` and `audit_filter_rules()` still dereference `e->rule.exe`, while the fsnotify mark can be freed on an independent lifetime path. This creates a use-after-free window during rule deletion. Fix this by unlinking the rule from the RCU-visible lists and invoking `synchronize_rcu()` before calling `audit_remove_mark_rule()` (and other rule removal helpers). This ensures that all existing RCU readers have exited the critical section before any underlying resources are destroyed.