tracing: Use trace_iterator_reset() in tracing_read_pipe()

Currently tracing_read_pipe() open codes trace_iterator_reset(). Just have
it use trace_iterator_reset() instead.

Link: https://lkml.kernel.org/r/20211210202616.64d432d2@gandalf.local.homeSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -6731,10 +6731,9 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 		cnt = PAGE_SIZE - 1;
 
 	/* reset all but tr, trace, and overruns */
-	memset_startat(iter, 0, seq);
+	trace_iterator_reset(iter);
 	cpumask_clear(iter->started);
 	trace_seq_init(&iter->seq);
-	iter->pos = -1;
 
 	trace_event_read_lock();
 	trace_access_lock(iter->cpu_file);