netfilter: ipset: Pass lockdep expression to RCU lists

ip_set_type_list is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of ip_set_type_mutex.

Hence, add corresponding lockdep expression to silence false-positive
warnings, and harden RCU lists.

Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>