cgroup: fix compile warning

commit 4f41fc59620f ("cgroup, kernfs: make mountinfo
 show properly scoped path for cgroup namespaces")
 added the following compile warning:

kernel/cgroup.c: In function ‘cgroup_show_path’:
kernel/cgroup.c:1634:15: warning: unused variable ‘ret’ [-Wunused-variable]
  int len = 0, ret = 0;
               ^
fix it.

Fixes: 4f41fc59620f ("cgroup, kernfs: make mountinfo show properly scoped path for cgroup namespaces")
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/cgroup.c

@@ -1631,7 +1631,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
 static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
 			    struct kernfs_root *kf_root)
 {
-	int len = 0, ret = 0;
+	int len = 0;
 	char *buf = NULL;
 	struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
 	struct cgroup *ns_cgroup;