tc35815: Fix return value of tc35815_do_interrupt when NAPI enabled

Return received count correctly even if tx completed at the same time.
Currently NAPI is disabled for this driver so this patch does not fix
any real problem.
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/tc35815.c

@@ -1592,7 +1592,12 @@ static int tc35815_do_interrupt(struct net_device *dev, u32 status)
 		lp->lstats.tx_ints++;
 		tc35815_txdone(dev);
 		netif_wake_queue(dev);
+#ifdef TC35815_NAPI
+		if (ret < 0)
+			ret = 0;
+#else
 		ret = 0;
+#endif
 	}
 	return ret;
 }