CVE-2026-98899: netfilter: ipset: mark the rcu locked areas properly

In the Linux kernel, the following vulnerability has been resolved:

netfilter: ipset: mark the rcu locked areas properly

When we bump the uref counter, there's no need to keep the rcu lock because the referred hash table can't disappear. Also, from the same reason in mtypegc we need the rcu lock and not a spinlock.