cgroup: net_cls: Move sock_update_classid() declaration to cls_cgroup.h

The only user of sock_update_classid() is net/socket.c which happens
to include cls_cgroup.h directly.

tj: Fix build breakage due to missing cls_cgroup.h inclusion in
    drivers/net/tun.c reported in linux-next by Stephen.
Signed-off-by: NDaniel Wagner <daniel.wagner@bmw-carit.de>
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: John Fastabend <john.r.fastabend@intel.com>
Cc: netdev@vger.kernel.org
Cc: cgroups@vger.kernel.org

drivers/net/tun.c

@@ -68,6 +68,7 @@
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
 #include <net/sock.h>
+#include <net/cls_cgroup.h>
 
 #include <asm/uaccess.h>
 

include/net/cls_cgroup.h

@@ -24,6 +24,8 @@ struct cgroup_cls_state
 	u32 classid;
 };
 
+extern void sock_update_classid(struct sock *sk);
+
 #ifdef CONFIG_NET_CLS_CGROUP
 static inline u32 task_cls_classid(struct task_struct *p)
 {
@@ -62,6 +64,10 @@ static inline u32 task_cls_classid(struct task_struct *p)
 }
 #endif
 #else
+static inline void sock_update_classid(struct sock *sk)
+{
+}
+
 static inline u32 task_cls_classid(struct task_struct *p)
 {
 	return 0;

include/net/sock.h

@@ -1486,14 +1486,6 @@ extern void *sock_kmalloc(struct sock *sk, int size,
 extern void sock_kfree_s(struct sock *sk, void *mem, int size);
 extern void sk_send_sigurg(struct sock *sk);
 
-#ifdef CONFIG_CGROUPS
-extern void sock_update_classid(struct sock *sk);
-#else
-static inline void sock_update_classid(struct sock *sk)
-{
-}
-#endif
-
 /*
  * Functions to fill in entries in struct proto_ops when a protocol
  * does not implement a particular function.