net: reduce structures when XFRM=n

ifdef out
* struct sk_buff::sp		(pointer)
* struct dst_entry::xfrm	(pointer)
* struct sock::sk_policy	(2 pointers)

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2725f4e..487e345 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -269,8 +269,9 @@
 		struct  dst_entry	*dst;
 		struct  rtable		*rtable;
 	};
+#ifdef CONFIG_XFRM
 	struct	sec_path	*sp;
-
+#endif
 	/*
 	 * This is the control buffer. It is free to use for every
 	 * layer. Please put your private variables there. If you
@@ -1864,6 +1865,18 @@
 	to->queue_mapping = from->queue_mapping;
 }
 
+#ifdef CONFIG_XFRM
+static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
+{
+	return skb->sp;
+}
+#else
+static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
+{
+	return NULL;
+}
+#endif
+
 static inline int skb_is_gso(const struct sk_buff *skb)
 {
 	return skb_shinfo(skb)->gso_size;