tracing: Use preempt_model_str()

Use preempt_model_str() instead of manually conducting the preemption
model.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20250314160810.2373416-10-bigeasy@linutronix.de

Author: Sebastian Andrzej Siewior

kernel/trace/trace.c

@@ -4100,12 +4100,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 		   entries,
 		   total,
 		   buf->cpu,
-		   preempt_model_none()      ? "server" :
-		   preempt_model_voluntary() ? "desktop" :
-		   preempt_model_full()      ? "preempt" :
-		   preempt_model_lazy()	     ? "lazy"    :
-		   preempt_model_rt()        ? "preempt_rt" :
-		   "unknown",
+		   preempt_model_str(),
 		   /* These are reserved for later use */
 		   0, 0, 0, 0);
 #ifdef CONFIG_SMP