cpuset: remove an unncessary forward declaration

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 72a0383..95f4b25 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -68,9 +68,6 @@
  */
 int number_of_cpusets __read_mostly;
 
-/* Forward declare cgroup structures */
-struct cgroup_subsys cpuset_subsys;
-
 /* See "Frequency meter" comments, below. */
 
 struct fmeter {