net: stmmac: fix INTR TBU status affecting irq count statistic

DMA channel status "Transmit buffer unavailable(TBU)" bit is not
considered as a successful dma tx. Hence, it should not affect
all the irq count statistic.

Fixes: 1103d3a5 ("net: stmmac: dwmac4: Also use TBU interrupt to clean TX path")
Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: Vijayakannan Ayyathurai <vijayakannan.ayyathurai@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c

@@ -172,11 +172,12 @@ int dwmac4_dma_interrupt(void __iomem *ioaddr,
 		x->rx_normal_irq_n++;
 		ret |= handle_rx;
 	}
-	if (likely(intr_status & (DMA_CHAN_STATUS_TI |
-		DMA_CHAN_STATUS_TBU))) {
+	if (likely(intr_status & DMA_CHAN_STATUS_TI)) {
 		x->tx_normal_irq_n++;
 		ret |= handle_tx;
 	}
+	if (unlikely(intr_status & DMA_CHAN_STATUS_TBU))
+		ret |= handle_tx;
 	if (unlikely(intr_status & DMA_CHAN_STATUS_ERI))
 		x->rx_early_irq++;