tilepro: Don't receive packets when the napi budget == 0

Processing any incoming packets with a with a napi budget of 0
is incorrect driver behavior.

This matters as netpoll will shortly call drivers with a budget of 0
to avoid receive packet processing happening in hard irq context.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/tile/tilepro.c

@@ -831,6 +831,9 @@ static int tile_net_poll(struct napi_struct *napi, int budget)
 
 	unsigned int work = 0;
 
+	if (budget <= 0)
+		goto done;
+
 	while (priv->active) {
 		int index = qup->__packet_receive_read;
 		if (index == qsp->__packet_receive_queue.__packet_write)