nfp: flower: fix port metadata conversion bug

Function nfp_flower_repr_get_type_and_port expects an enum nfp_repr_type
return value but, if the repr type is unknown, returns a value of type
enum nfp_flower_cmsg_port_type.  This means that if FW encodes the port
ID in a way the driver does not understand instead of dropping the frame
driver may attribute it to a physical port (uplink) provided the port
number is less than physical port count.

Fix this and ensure a net_device of NULL is returned if the repr can not
be determined.

Fixes: 1025351 ("nfp: add flower app")
Signed-off-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/main.c

@@ -80,7 +80,7 @@ nfp_flower_repr_get_type_and_port(struct nfp_app *app, u32 port_id, u8 *port)
 			return NFP_REPR_TYPE_VF;
 	}
 
-	return NFP_FLOWER_CMSG_PORT_TYPE_UNSPEC;
+	return __NFP_REPR_TYPE_MAX;
 }
 
 static struct net_device *
@@ -91,6 +91,8 @@ nfp_flower_repr_get(struct nfp_app *app, u32 port_id)
 	u8 port = 0;
 
 	repr_type = nfp_flower_repr_get_type_and_port(app, port_id, &port);
+	if (repr_type > NFP_REPR_TYPE_MAX)
+		return NULL;
 
 	reprs = rcu_dereference(app->reprs[repr_type]);
 	if (!reprs)