net: caif: fix erroneous return value

The cfrfml_receive() function might return positive value EPROTO
Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/caif/cfrfml.c

@@ -159,7 +159,7 @@ static int cfrfml_receive(struct cflayer *layr, struct cfpkt *pkt)
 		tmppkt = NULL;
 
 		/* Verify that length is correct */
-		err = EPROTO;
+		err = -EPROTO;
 		if (rfml->pdu_size != cfpkt_getlen(pkt) - RFM_HEAD_SIZE + 1)
 			goto out;
 	}