netns xfrm: add netns boilerplate

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
new file mode 100644
index 0000000..1cb0024
--- /dev/null
+++ b/include/net/netns/xfrm.h
@@ -0,0 +1,7 @@
+#ifndef __NETNS_XFRM_H
+#define __NETNS_XFRM_H
+
+struct netns_xfrm {
+};
+
+#endif