[NET]: netns compilation speedup

This patch speedups compilation when net_namespace.h is changed.

Signed-off-by: Denis V. Lunev <[e-mail]>
Acked-by: "Eric W. Biederman" <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/pkt_cls.h

···
 #define __NET_PKT_CLS_H
 
 #include <linux/pkt_cls.h>
-#include <net/net_namespace.h>
 #include <net/sch_generic.h>
 #include <net/act_api.h>
 
···
 }
 
 #ifdef CONFIG_NET_CLS_IND
+#include <net/net_namespace.h>
+
 static inline int
 tcf_change_indev(struct tcf_proto *tp, char *indev, struct rtattr *indev_tlv)
 {

include/net/sock.h

···
 #include <asm/atomic.h>
 #include <net/dst.h>
 #include <net/checksum.h>
-#include <net/net_namespace.h>
 
 /*
  * This structure really needs to be cleaned up.
···
 
 struct sock;
 struct proto;
+struct net;
 
 /**
  *	struct sock_common - minimal network layer representation of sockets