perf/cgroup: Remove perf_put_cgroup()

Commit 5a17f543 ("cgroup: improve css_from_dir() into css_tryget_from_dir()")
removed perf_tryget_cgroup(), so let's also remove perf_put_cgroup().
Signed-off-by: NZefan Li <lizefan@huawei.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

kernel/events/core.c

@@ -391,14 +391,9 @@ perf_cgroup_match(struct perf_event *event)
 				    event->cgrp->css.cgroup);
 }
 
-static inline void perf_put_cgroup(struct perf_event *event)
-{
-	css_put(&event->cgrp->css);
-}
-
 static inline void perf_detach_cgroup(struct perf_event *event)
 {
-	perf_put_cgroup(event);
+	css_put(&event->cgrp->css);
 	event->cgrp = NULL;
 }