stmmac: fix a bug while checking the HW cap reg (v2)

The patch fixes a bug while checking the HW cap reg
on old MAC10/100 where this feature is not available.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -812,9 +812,10 @@ static u32 stmmac_get_synopsys_id(struct stmmac_priv *priv)
  */
 static int stmmac_get_hw_features(struct stmmac_priv *priv)
 {
-	u32 hw_cap = priv->hw->dma->get_hw_feature(priv->ioaddr);
+	u32 hw_cap = 0;
+	if (priv->hw->dma->get_hw_feature) {
+		hw_cap = priv->hw->dma->get_hw_feature(priv->ioaddr);
 
-	if (likely(hw_cap)) {
 		priv->dma_cap.mbps_10_100 = (hw_cap & DMA_HW_FEAT_MIISEL);
 		priv->dma_cap.mbps_1000 = (hw_cap & DMA_HW_FEAT_GMIISEL) >> 1;
 		priv->dma_cap.half_duplex = (hw_cap & DMA_HW_FEAT_HDSEL) >> 2;