remove unused pid_max in trace.h

euler inclusion
category: bugfix
bugzilla: 14007
CVE: NA

-------------------------------------------------

In commit b8f8307ae1e9 ("pid_ns: Make pid_max per namespace"), pid_max
is made per namespace, so global pid_max in trace.h is unused now.
Remove it.
Signed-off-by: Nluojiajun <luojiajun3@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/trace/trace.h

@@ -701,8 +701,6 @@ extern unsigned long tracing_thresh;
 
 /* PID filtering */
 
-extern int pid_max;
-
 bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,
 			     pid_t search_pid);
 bool trace_ignore_this_task(struct trace_pid_list *filtered_pids,