sky2: 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/marvell/sky2.c

@@ -2735,6 +2735,9 @@ static int sky2_status_intr(struct sky2_hw *hw, int to_do, u16 idx)
 	unsigned int total_bytes[2] = { 0 };
 	unsigned int total_packets[2] = { 0 };
 
+	if (to_do <= 0)
+		return work_done;
+
 	rmb();
 	do {
 		struct sky2_port *sky2;