rv: Merge struct rv_monitor_def into struct rv_monitor

rv: Merge struct rv_monitor_def into struct rv_monitor

Each struct rv_monitor has a unique struct rv_monitor_def associated with
it. struct rv_monitor is statically allocated, while struct rv_monitor_def
is dynamically allocated.

This makes the code more complicated than it should be:

  - Lookup is required to get the associated rv_monitor_def from rv_monitor

  - Dynamic memory allocation is required for rv_monitor_def. This is
    harder to get right compared to static memory. For instance, there is
    an existing mistake: rv_unregister_monitor() does not free the memory
    allocated by rv_register_monitor(). This is fortunately not a real
    memory leak problem, as rv_unregister_monitor() is never called.

Simplify and merge rv_monitor_def into rv_monitor.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/194449c00f87945c207aab4c96920c75796a4f53.1753378331.git.namcao@linutronix.de
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>