sock: Hide unused variable when !CONFIG_PROC_FS.

When CONFIG_PROC_FS is disabled, we will not use the prot_inuse
counter. This adds an #ifdef to hide the variable definition in
that case. This is not a bugfix. But we can save bytes when there
are many network namespace.

Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NMartin Zhang <zhangjunweimartin@didichuxing.com>
Signed-off-by: NTonghao Zhang <zhangtonghao@didichuxing.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/netns/core.h

@@ -13,8 +13,8 @@ struct netns_core {
 
 #ifdef CONFIG_PROC_FS
 	int __percpu *sock_inuse;
-#endif
 	struct prot_inuse __percpu *prot_inuse;
+#endif
 };
 
 #endif