r6040: only disable RX interrupt if napi_schedule_prep is successful

When receiving the first RX interrupt before the internal call
to napi_schedule_prep is successful the RX interrupt gets disabled
and is never enabled again as the poll function never gets executed.
Signed-off-by: Michael Thalmeier <Michael.Thalmeier@sigmatek.at>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/r6040.c

@@ -677,9 +677,11 @@ static irqreturn_t r6040_interrupt(int irq, void *dev_id)
 		if (status & RX_FIFO_FULL)
 			dev->stats.rx_fifo_errors++;
 
+		if (likely(napi_schedule_prep(&lp->napi))) {
 			/* Mask off RX interrupt */
 			misr &= ~RX_INTS;
-		napi_schedule(&lp->napi);
+			__napi_schedule(&lp->napi);
+		}
 	}
 
 	/* TX interrupt request */