can: use correct NET_RX_ return values

Dropped skb's should be documented by an appropriate return value.
Use the correct NET_RX_DROP and NET_RX_SUCCESS values for that reason.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/can/af_can.c b/net/can/af_can.c
index f9c027b..ef1c43a 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -686,11 +686,11 @@
 		can_stats.matches_delta++;
 	}
 
-	return 0;
+	return NET_RX_SUCCESS;
 
 drop:
 	kfree_skb(skb);
-	return 0;
+	return NET_RX_DROP;
 }
 
 /*