iwlwifi: mvm: fix locking in iwl_mvm_ipv6_addr_change

	struct inet6_ifaddr *ifa;

	int idx = 0;

	read_lock(&idev->lock);

	read_lock_bh(&idev->lock);

	list_for_each_entry(ifa, &idev->addr_list, if_list) {

		mvmvif->target_ipv6_addrs[idx] = ifa->addr;

		idx++;

		if (idx >= IWL_PROTO_OFFLOAD_NUM_IPV6_ADDRS)

			break;

	}

	read_unlock(&idev->lock);

	read_unlock_bh(&idev->lock);

	mvmvif->num_target_ipv6_addrs = idx;

}