xfrm: Const'ify selector argument to xfrm_selector_match()

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 46f4470..567f08b 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -845,7 +845,7 @@
 	return port;
 }
 
-extern int xfrm_selector_match(struct xfrm_selector *sel,
+extern int xfrm_selector_match(const struct xfrm_selector *sel,
 			       const struct flowi *fl,
 			       unsigned short family);