CVE-2025-40232

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

rv: Fully convert enabled_monitors to use list_head as iterator

The callbacks in enabled_monitors_seq_ops are inconsistent. Some treat the
iterator as struct rv_monitor *, while others treat the iterator as struct
list_head *.

This causes a wrong type cast and crashes the system as reported by Nathan.

Convert everything to use struct list_head * as iterator. This also makes
enabled_monitors consistent with available_monitors.