netns xfrm: pass netns with KM notifications

SA and SPD flush are executed with NULL SA and SPD respectively, for
these cases pass netns explicitly from userspace socket.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index e027179..52e784f 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -256,6 +256,7 @@
 	u32	seq;
 	u32	pid;
 	u32	event;
+	struct net *net;
 };
 
 struct net_device;