[VETH]: move veth.h to include/linux

Move veth.h from net/ to linux/ since it is a user api, and add it to
user header processing Kbuild.

[ Use header-y as suggested by Sam Ravnborg.  -DaveM ]

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index fdd1e03..43af9e9 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -15,7 +15,7 @@
 
 #include <net/dst.h>
 #include <net/xfrm.h>
-#include <net/veth.h>
+#include <linux/veth.h>
 
 #define DRV_NAME	"veth"
 #define DRV_VERSION	"1.0"