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 <[e-mail]>
Signed-off-by: Martin Zhang <[e-mail]>
Signed-off-by: Tonghao Zhang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/netns/core.h

···
 
 #ifdef CONFIG_PROC_FS
 	int __percpu *sock_inuse;
-#endif
 	struct prot_inuse __percpu *prot_inuse;
+#endif
 };
 
 #endif