net: fix socket memcg build with !CONFIG_NET

There is still a build bug with the sock memcg code, that triggers
with !CONFIG_NET, that survived my series of randconfig builds.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 97fc0ad..0e7a9b0 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -922,7 +922,7 @@
 #define sk_refcnt_debug_release(sk) do { } while (0)
 #endif /* SOCK_REFCNT_DEBUG */
 
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_NET)
 extern struct jump_label_key memcg_socket_limit_enabled;
 static inline struct cg_proto *parent_cg_proto(struct proto *proto,
 					       struct cg_proto *cg_proto)