cgroup: Make cgroup_debug static

Make cgroup_debug static since it's only used in cgroup.c
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/cgroup/cgroup-internal.h

@@ -12,7 +12,6 @@
 #define TRACE_CGROUP_PATH_LEN 1024
 extern spinlock_t trace_cgroup_path_lock;
 extern char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
-extern bool cgroup_debug;
 extern void __init enable_debug_cgroup(void);
 
 /*

kernel/cgroup/cgroup.c

@@ -96,7 +96,7 @@ EXPORT_SYMBOL_GPL(css_set_lock);
 
 DEFINE_SPINLOCK(trace_cgroup_path_lock);
 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
-bool cgroup_debug __read_mostly;
+static bool cgroup_debug __read_mostly;
 
 /*
  * Protects cgroup_idr and css_idr so that IDs can be released without