sfc: 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/sfc/ef10.c

@@ -1955,6 +1955,9 @@ static int efx_ef10_ev_process(struct efx_channel *channel, int quota)
 	int tx_descs = 0;
 	int spent = 0;
 
+	if (quota <= 0)
+		return spent;
+
 	read_ptr = channel->eventq_read_ptr;
 
 	for (;;) {

drivers/net/ethernet/sfc/farch.c

@@ -1248,6 +1248,9 @@ int efx_farch_ev_process(struct efx_channel *channel, int budget)
 	int tx_packets = 0;
 	int spent = 0;
 
+	if (budget <= 0)
+		return spent;
+
 	read_ptr = channel->eventq_read_ptr;
 
 	for (;;) {