rv: Fix wrong type cast in monitors_show()

Argument 'p' of monitors_show() is not a pointer to struct rv_monitor, it
is actually a pointer to the list_head inside struct rv_monitor. Therefore
it is wrong to cast 'p' to struct rv_monitor *.

This wrong type cast has been there since the beginning. But it still
worked because the list_head was the first field in struct rv_monitor_def.
This is no longer true since commit 24cbfe1 ("rv: Merge struct
rv_monitor_def into struct rv_monitor") moved the list_head, and this wrong
type cast became a functional problem.

Properly use container_of() instead.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/35e49e97696007919ceacf73796487a2e15a3d02.1753625621.git.namcao@linutronix.de
Fixes: 24cbfe1 ("rv: Merge struct rv_monitor_def into struct rv_monitor")
Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: covanam

kernel/trace/rv/rv.c

@@ -458,7 +458,7 @@ static int create_monitor_dir(struct rv_monitor *mon, struct rv_monitor *parent)
  */
 static int monitors_show(struct seq_file *m, void *p)
 {
-	struct rv_monitor *mon = p;
+	struct rv_monitor *mon = container_of(p, struct rv_monitor, list);
 
 	if (mon->parent)
 		seq_printf(m, "%s:%s\n", mon->parent->name, mon->name);