xfrm: Mark flowi arg to xfrm_selector_match() const.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 2328532..b965ad7 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -843,7 +843,8 @@
 	return port;
 }
 
-extern int xfrm_selector_match(struct xfrm_selector *sel, struct flowi *fl,
+extern int xfrm_selector_match(struct xfrm_selector *sel,
+			       const struct flowi *fl,
 			       unsigned short family);
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM