net: stmmac: dwxgmac: Fix the undefined burst setting

Undefined burst shall only be set if pdata asks to.
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c

@@ -91,11 +91,11 @@ static void dwxgmac2_dma_axi(void __iomem *ioaddr, struct stmmac_axi *axi)
 	value |= (axi->axi_rd_osr_lmt << XGMAC_RD_OSR_LMT_SHIFT) &
 		XGMAC_RD_OSR_LMT;
 
+	if (!axi->axi_fb)
+		value |= XGMAC_UNDEF;
+
 	value &= ~XGMAC_BLEN;
 	for (i = 0; i < AXI_BLEN; i++) {
-		if (axi->axi_blen[i])
-			value &= ~XGMAC_UNDEF;
-
 		switch (axi->axi_blen[i]) {
 		case 256:
 			value |= XGMAC_BLEN256;